Separation System

Abstract

One embodiment of the present invention is a separation system comprising: a separation unit that separates a first signal with a first wavelength and a second signal with a second wavelength from an inputted optical signal, said second wavelength being a wavelength other than the first wavelength; and a detection unit that detects the intensity of the second signal.

Description

[Technical Field]

[0001] The present invention relates to the art of separation systems. [Background technology]

[0002] In recent years, there has been a demand for the realization of a transparent, low-latency optical access network using a Photonic Gateway (hereinafter referred to as "PG") (see, for example, Non-Patent Document 1). A plurality of user devices are connected to a PG, and a wavelength to be used is set for each user device. In the following description, when an optical signal flows from a source to a destination, a position relatively closer to the source is called a "preceding stage," and a position relatively closer to the destination is called a "rear stage." [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "A new system architecture for realizing all-photonics networks," Journal of the Institute of Electronics, Information and Communication Engineers, Vol. 104, No. 5, pp. 471-477, 2021.<URL:https: / / www.journal.ieice.org / bin / pdf_link.php?fname=k104_5_471&lang=J&year=2021> Summary of the Invention [Problem to be solved by the invention]

[0004] A transparent network must not allow the passage of at least one type of light (hereinafter referred to as "non-compliant light"), which is either of an unacceptable intensity or contains wavelengths other than those specified. Non-compliant light may be input from, for example, a user device that is not under control. However, PG-based networks have not yet realized the function to detect non-compliant signals or to prevent them from passing (stopping them). This problem is not limited to PG-based networks, but is common to all transparent networks.

[0005] In view of the above circumstances, the present invention aims to provide a technology that can detect incompatible signals in a transparent network and prevent incompatible signals from being transmitted to downstream devices. [Means for solving the problem]

[0006] One aspect of the present invention is a separation system comprising a separation unit that separates an input optical signal into a first signal of a first wavelength and a second signal of a second wavelength that is a wavelength other than the first wavelength, and a detection unit that detects the intensity of the second signal.

[0007] One aspect of the present invention is a separation system comprising a separation unit that separates an input optical signal into a first signal of a first wavelength and a second signal of a second wavelength that is a wavelength other than the first wavelength, and a discard unit that discards the second signal so that it does not mix with the first signal. [Effects of the Invention]

[0008] The present invention makes it possible to detect non-compliant signals in a transparent network and to prevent non-compliant signals from being transmitted to downstream devices. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of a system configuration of a first embodiment (light sorting system 10a) of a light sorting system 10 of the present invention. [Figure 2] FIG. 10 is a diagram showing an outline of the intensity of an optical signal of each wavelength in a separation system 11a. [Figure 3] 10 is a diagram showing an outline of the suppression ratio of a filter in the separation unit 21. FIG. [Figure 4] FIG. 1 is a diagram showing a first specific example of the configuration of a separation system 11a. [Figure 5] FIG. 10 is a diagram showing a second specific example of the configuration of the separation system 11a. [Figure 6] FIG. 10 is a diagram showing a fifth specific example of the configuration of the separation system 11a. [Figure 7] FIG. 10 is a diagram showing a sixth specific example of the configuration of the separation system 11a. [Figure 8] FIG. 10 is a diagram showing a seventh specific example of the configuration of the separation system 11a. [Figure 9] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 10] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 11] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 12] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 13] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 14] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 15] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 16] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 17] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 18] 1 is a diagram showing a specific example of the positional relationship of each device in a first embodiment of the light sorting system 10 (light sorting system 10a). FIG. [Figure 19] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 20] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 21] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 22] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 23] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 24] FIG. 10 is a diagram illustrating a configuration example using an optical fuse. [Figure 25] FIG. 10 is a diagram illustrating a configuration example using an optical monitor. [Figure 26] FIG. 10 is a diagram illustrating a configuration example using an optical monitor. [Figure 27] FIG. 10 is a diagram showing a first configuration example in which a separation section 21 is configured using an FBG (Fiber Bragg Grating). [Figure 28] FIG. 10 is a diagram showing a second configuration example in which the separation section 21 is configured using an FBG. [Figure 29] FIG. 10 is a diagram showing a third configuration example in which the separation unit 21 is configured using an FBG. [Figure 30] FIG. 10 is a diagram showing a fourth configuration example in which the separation section 21 is configured using an FBG. [Figure 31] FIG. 10 is a diagram showing a fifth configuration example in which the separation unit 21 is configured using an FBG. [Figure 32] FIG. 10 is a diagram showing a sixth configuration example in which the separation unit 21 is configured using an FBG. [Figure 33] FIG. 10 is a diagram showing a seventh configuration example in which the separation section 21 is configured using an FBG. [Figure 34]FIG. 10 is a diagram showing an eighth configuration example in which the separation section 21 is configured using an FBG. [Figure 35] FIG. 10 is a diagram showing a first configuration example in which the separation unit 21 is configured using a TFF (Thin Film Filter). [Figure 36] FIG. 10 is a diagram showing a second configuration example in which the separation unit 21 is configured using a TFF. [Figure 37] FIG. 10 is a diagram showing a third configuration example in which the separation unit 21 is configured using a TFF. [Figure 38] FIG. 10 is a diagram illustrating a configuration example of a TFF 214 for oblique incidence. [Figure 39] FIG. 10 is a diagram showing a fourth configuration example in which the separation unit 21 is configured using a TFF. [Figure 40] FIG. 10 is a diagram showing a fifth configuration example in which the separation unit 21 is configured using a TFF. [Figure 41] FIG. 10 is a diagram showing a sixth configuration example in which the separation unit 21 is configured using a TFF. [Figure 42] FIG. 10 is a diagram showing a seventh configuration example in which the separation unit 21 is configured using a TFF. [Figure 43] FIG. 10 is a diagram showing an eighth configuration example in which the separation unit 21 is configured using a TFF. [Figure 44] FIG. 10 is a diagram showing a first configuration example in which the separating section 21 is configured using an AWG (Arrayed-Waveguide Grating). [Figure 45] FIG. 10 is a diagram showing a second configuration example in which the separating section 21 is configured using an AWG. [Figure 46] FIG. 10 is a diagram showing a third configuration example in which the separating section 21 is configured using an AWG. [Figure 47] FIG. 10 is a diagram showing a fifth configuration example in which the separating section 21 is configured using an AWG. [Figure 48] FIG. 10 is a diagram showing a sixth configuration example in which the separating section 21 is configured using an AWG. [Figure 49] FIG. 10 is a diagram showing a seventh configuration example in which the separating section 21 is configured using an AWG. [Figure 50] FIG. 10 is a diagram showing an eighth configuration example in which the separating section 21 is configured using an AWG. [Figure 51]FIG. 13 is a diagram showing a ninth configuration example in which the separating section 21 is configured using an AWG. [Figure 52] FIG. 19 is a diagram illustrating a tenth configuration example in which the separating section 21 is configured using an AWG. [Figure 53] FIG. 12 is a diagram illustrating a twelfth configuration example in which the separating section 21 is configured using an AWG. [Figure 54] FIG. 13 is a diagram illustrating a thirteenth configuration example in which the separating section 21 is configured using an AWG. [Figure 55] FIG. 14 is a diagram illustrating a fourteenth configuration example in which the separating section 21 is configured using an AWG. [Figure 56] FIG. 10 is a diagram showing a modification of the first embodiment of the separation system 11a. [Figure 57] FIG. 10 is a diagram showing a modification of the first embodiment of the separation system 11a. [Figure 58] FIG. 10 is a diagram showing a modification of the first embodiment of the separation system 11a. [Figure 59] FIG. 10 is a diagram showing a first configuration example in which a separating section 21 in a modified example is configured using an AWG. [Figure 60] FIG. 10 is a diagram showing a second configuration example in which the separating section 21 in the modified example is configured using an AWG. [Figure 61] FIG. 10 is a diagram showing a modified example of an AWG. [Figure 62] FIG. 10 is a diagram showing an example of the configuration of a separator 21 configured using a modified AWG. [Figure 63] FIG. 10 is a diagram showing an example of the configuration of a separator 21 configured using a modified AWG. [Figure 64] 10 is a diagram showing a specific example of a separation unit 21 configured using a reflective diffraction grating. FIG. [Figure 65] 10 is a diagram showing a specific example of a separation unit 21 configured using a reflective diffraction grating. FIG. [Figure 66] FIG. 10 is a diagram showing a first configuration example in which a separator 21 is configured using a waveguide-type ring resonator. [Figure 67] FIG. 10 is a diagram showing a second configuration example in which a separator 21 is configured using a waveguide-type ring resonator. [Figure 68]FIG. 10 is a diagram showing a first configuration example in which the separating section 21 is configured using a lattice-type optical filter. [Figure 69] FIG. 10 is a diagram showing a second configuration example in which the separating section 21 is configured using a lattice type optical filter. [Figure 70] 10 is a diagram showing a specific example of the configuration of the separator 21 when the separator 21 is configured using a separator with high polarization dependency. FIG. [Figure 71] FIG. 10 is a diagram showing an example of a system configuration of a second embodiment (light sorting system 10b) of the light sorting system 10 of the present invention. [Figure 72] FIG. 10 is a diagram showing a first specific example of the configuration of a separation system 11b. [Figure 73] FIG. 11 is a diagram showing a third specific example of the configuration of the separation system 11b. [Figure 74] FIG. 10 is a diagram illustrating an example of a system configuration of a third embodiment (light sorting system 10c) of the light sorting system 10 of the present invention. [Figure 75] FIG. 10 is a diagram illustrating an example of a system configuration of a fourth embodiment (light sorting system 10d) of the light sorting system 10 of the present invention. [Figure 76] FIG. 10 is a diagram showing a first specific example of the configuration of a separation system 11d. [Figure 77] FIG. 11 is a diagram showing a third specific example of the configuration of a separation system 11d. [Figure 78] FIG. 11 shows a modified example of the second embodiment of the separation system 11b. [Figure 79] FIG. 11 shows a modification of the fourth embodiment of the separation system 11d. [Figure 80] FIG. 10 is a diagram showing another specific example of the configuration of the separation system 11a. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. The optical distribution system 10 of the present invention is a device that outputs a desired signal from among input optical signals and distributes it to a destination. The optical distribution system 10 is used in a transparent network. A specific example of a transparent network is a PG network. Below, as an embodiment of the optical distribution system 10, the optical distribution system 10 used in a PG is described. However, as described above, the optical distribution system 10 may be applied to any transparent network, and does not need to be limited to application to a PG network as described below. Furthermore, in the optical distribution system 10 described below, each separation system 11 is applied in a mechanism for instructing wavelengths to user equipment, but the separation system 11 of the present invention does not necessarily need to be limited to application in such a mechanism.

[0011] One or more user devices are connected to one side of the PG. A specific wavelength is set by the PG for each user device under the control of the PG. Each user device under the control of the PG transmits an optical signal at the set wavelength according to specific criteria such as signal strength. The user device with which the communication is made (hereinafter referred to as the "opposite device") is located on the other side of the PG. The optical signal transmitted from each user device is output to an appropriate route by the PG's optical distribution device and transmitted to the destination opposite device. In the following description, the term "first side" refers to a position relatively close to the opposite device, and the term "second side" refers to a position relatively close to the user device that is the source of the optical signal to be processed.

[0012] [First embodiment] 1 is a diagram showing an example of a system configuration of a first embodiment (light sorting system 10a) of a light sorting system 10 of the present invention. The light sorting system 10a includes a separation system 11a and a light sorting device 40. The separation system 11a includes a separation device 20 and a blocking device 30.

[0013] The demultiplexer 20 processes the optical signal input to the demultiplexer (hereinafter referred to as the "demultiplexed input signal"). In the following description, the desired wavelength indicates a suitable wavelength range, and the remaining wavelength indicates a wavelength range other than the desired wavelength.

[0014] The suitable wavelength range varies depending on the wavelengths that the user device can use. For example, at the time of initial connection (when no wavelengths are set in the user device), the suitable wavelength range is the wavelength range that can be used for the initial connection, and after a wavelength is set in the user device after the initial connection, the set wavelength range becomes the suitable wavelength range.

[0015] 2 is a schematic diagram of the desired wavelength and the remaining wavelengths when the desired wavelength in the separation system 11a is one wavelength. Note that the desired wavelength may be a plurality of wavelengths, as in the examples described later. The desired signal is an optical signal whose intensity is below a threshold for matching intensity, whose intensity of the remaining wavelength components is below a threshold for matching wavelength, or both. Note that a matching optical signal is also referred to as "matching light" in the following description. A residual signal is an optical signal whose intensity is equal to or exceeds a threshold value for intensity, or whose intensity of a residual wavelength component is equal to or exceeds a threshold value for wavelength. Note that in the following description, non-compliant optical signals will also be referred to as "non-compliant light."

[0016] An example of a threshold value for intensity that is suitable may be a value that does not cause damage to downstream devices such as the optical fiber, the optical distribution device that constitutes the optical distribution system, and the corresponding device of the user device, such as 10 dBm (10 mW).An example of a threshold value for wavelength that is suitable may be a value that allows for an acceptable impact on the communication or communication quality of other user devices that use the residual wavelength as the desired wavelength, such as a value where the intensity of the residual wavelength of a signal input or output to a demultiplexer is sufficiently smaller than the OFF level when the other user uses ON / OFF modulation, or a value where the intensity of the residual wavelength after blocking due to the blocking ability of the residual wavelength in a demultiplexer that multiplexes the signal from the other user is sufficiently small, such as -20 dBm (0.01 mW).An example of a threshold value for wavelength that is suitable may be a value where the ratio of the intensity of the residual wavelength to the intensity of the desired wavelength is sufficiently small, such as -20 dB (1 / 100) or less.

[0017] The demultiplexer 20 wavelength-demultiplexes an optical signal of a desired wavelength (hereinafter referred to as a "desired demultiplexed signal") from an optical signal of a remaining wavelength (hereinafter referred to as a "residual demultiplexed signal") from a demultiplexed input signal. For example, the demultiplexer 20 may be configured to include a demultiplexing unit 21 and a detecting unit 22, as described below.

[0018] In the demultiplexing process in the demultiplexing section 21 of the demultiplexing device 20 of the demultiplexing system 11a, a desired signal and a residual signal are wavelength-separated from a demultiplexed input signal. The optical signal separated as the desired signal in the demultiplexing process is hereinafter referred to as the "desired demultiplexed signal." The optical signal separated as the residual signal is hereinafter referred to as the "residual demultiplexed signal." Depending on the characteristics (suppression ratio, cutoff power) of the filter used in the demultiplexing process, if there is a residual wavelength component, the desired demultiplexed signal may be slightly mixed with the residual wavelength component, and if there is a desired wavelength component, the residual demultiplexed signal may be slightly mixed with the desired wavelength component. However, if the ratio of the desired signal in the demultiplexed input signal is significantly high, the desired signal will account for the majority of the desired demultiplexed signal and the residual demultiplexed signal, and if the ratio of the residual signal in the demultiplexed input signal is significantly high, the residual signal will account for the majority of the desired demultiplexed signal and the residual demultiplexed signal. This can also occur depending on the filter's suppression ratio.

[0019] 3 is a diagram illustrating an outline of wavelength separation by the separation unit 21 of the separation device 20 of the separation system 11a. The optical intensity of the desired wavelength component in the optical signal (separation input signal) before separation by the separation unit 21 is defined as A, the proportion of the desired wavelength component separated as a residual separation signal as α, the proportion separated as a desired separation signal as (1-α), the optical intensity of the residual wavelength component in the optical signal (separation input signal) before separation by the separation unit 21 as B, the proportion of the residual wavelength component separated as a desired separation wavelength as β, and the proportion of the residual signal separated as a residual separation signal as (1-β).

[0020] In the case of Figure 3, the optical intensity of the residual separated signal after separation by the separation unit 21 is αA + (1 - β)B. The optical intensity of the desired separated signal after separation by the separation unit 21 is (1 - α)A + βB. The value obtained by multiplying the optical intensity of the desired separated signal by α / (1 - α) is subtracted from the optical intensity of the residual separated signal. As a result, the intensity B of the residual signal is expressed as follows:

[0021] (αA+(1-β)B)-α / (1-α)((1-α)A+βB)=(1-β)B-β / (1-α)B=(1-β(1-1 / (1-α))B≒B Note that α<<1, β<<1, and (1-β(1-1 / (1-α))) is approximated to 1.

[0022] If the intensity of the optical signal before being separated in the separation unit 21 is obtained by the optical monitor 92, the intensity B of the residual signal may be expressed as follows:

[0023] B≒(1-α)B=(αA+B)-α·(A+B) The strength B of the residual signal before separation in the separation unit 21 may be expressed as follows: Intensity of mismatched light before separation B = (output value of the detection unit) - (suitable optical output ratio α of the non-suitable optical output port of the demultiplexer) / (suitable optical output ratio (1-α) of the suitable optical output port of the demultiplexer) × (monitor value of the suitable optical output port of the demultiplexer) = (output value of the detection unit) - (suitable optical output ratio α of the non-suitable optical output port of the separator) / (suitable optical output ratio (1-α) of the suitable optical output port of the separator) × {(suitable optical output ratio (1-α) of the suitable optical output port of the separator) × (suitable optical intensity A before separation) + (non-suitable optical output ratio β of the suitable optical output port of the separator) × (non-suitable optical intensity B before separation)} ≒ (Detection unit output value) - (Compliant optical output ratio α of the non-compliant optical output port of the separator) / (Compliant optical output ratio (1-α) of the compatible optical output port of the separator) × {(Compliant optical output ratio (1-α) of the compatible optical output port of the separator) × (Compliant light intensity A before separation)} = (output value of the detection unit) - (matching light output ratio α of the non-matching light side output port in the separation unit) × (matching light intensity A before separation)

[0024] It is assumed that there are sufficiently few optical signals (residual signals) other than the light of the desired wavelength, and the suppression ratio of the residual optical signals is ignored. In other words, it is assumed that the light other than the matching wavelength before separation is sufficiently weaker than the light of the matching wavelength, and the imperfection of the suppression of the light other than the matching wavelength in the separation unit 21 is ignored.

[0025] If the strength of the residual separated signal is equal to or greater than a predetermined strength, the separated input signal or the desired separated signal separated from the separated input signal is blocked in the separation system 11a including the blocking device 30. Note that the predetermined strength value (threshold value) for the wavelength may be set in consideration of the characteristics of the filter so that the leakage of the residual signal into the desired separated signal is equal to or less than the predetermined strength.

[0026] In the following description, "predetermined intensity" refers to an acceptable high intensity when it relates to the intensity of the signal light, such as a value that increases the risk of damaging downstream equipment, or an intensity that may damage telecommunications facilities connected to users or other telecommunications carriers as defined in Article 19 of the Regulations for Telecommunications Facilities for Business Use (Damage Prevention). The above-mentioned predetermined intensity value (threshold) for wavelength may be, for example, an intensity below the noise level or below the OFF level in the case of IM-DD.

[0027] Even if the separated input signal contains only an optical signal of the desired wavelength (does not contain signals of the remaining wavelengths), if the intensity of the separated input signal exceeds an appropriate value (is equal to or greater than a predetermined intensity), the separated input signal or the optical signal (desired separated signal) separated from the separated input signal will be blocked in the separation system 11a including the blocking device 30.

[0028] The demultiplexer 20 detects the optical intensity of the separated residual demultiplexed signal. When the demultiplexer 20 detects that the residual demultiplexed signal has an optical intensity equal to or greater than a predetermined value, it outputs a control signal to the blocking device 30, instructing it to block the optical signal input to the blocking device 30. When the blocking device 30 does not block the optical signal (i.e., does not receive a control signal indicating blocking), it passes the input optical signal. The optical signal that passes through the blocking device 30 is input to a device connected downstream of the blocking device 30. When the blocking device 30 receives a control signal indicating blocking from the demultiplexer 20, it blocks the optical signal input to its own device. In this case, the optical signal input to the blocking device 30 is not input to a device connected downstream. As a result, the desired signal included in the blocked optical signal (the optical signal that contained the non-compliant optical signal) does not reach its destination. In addition, when the cutoff device 30 cuts off the power by inputting a control signal indicating that the power should be cut off, the cutoff device 30 may be configured to continue cutting off the power until a control signal indicating that the power should be released is input, even if the control signal indicating that the power should be cut off is no longer input, or may be configured to continue cutting off the power as long as the control signal indicating that the power should be cut off is input, and to release the power when the control signal is no longer input.

[0029] The demultiplexer 20 may be configured to communicate with the control unit using any signal. For example, the demultiplexer 20 may superimpose the user signal onto an optical signal (main signal) used by the user signal, and communicate with the control unit using an optical signal with the wavelength used for the initial connection (when no wavelength has been set in the user device). After a wavelength has been set in the user device, the demultiplexer 20 may communicate with the control unit using an optical signal with that wavelength (desired wavelength). Alternatively, the demultiplexer 20 may communicate with the control unit using an optical signal with a wavelength different from the wavelengths described above at each timing. The demultiplexer 20 may also be configured to communicate with the control unit using a different carrier or line (a different route from the main signal) from the optical signal used by the user device. In such cases, the demultiplexer 20 may communicate with the control unit using an optical signal or electrical signal with a wavelength different from the wavelength used for the initial connection or the set wavelength described above.

[0030] The above-mentioned communication between the separation device 20 and the control unit can be similarly applied to the communication between the interruption device 30 and the control unit, which will be described later, and also to the communication between the separation device 20 and the interruption device 30. However, the communication between the separation device 20 and the control unit, the communication between the interruption device 30 and the control unit, and the communication between the separation device 20 and the interruption device 30 may be partially realized by the same communication means, or may be realized by different communication means, or may all be realized by the same communication means.

[0031] The optical distribution device 40 distributes optical signals input to the device itself, and outputs the signals from a port according to the destination (to the destination device or a path connected to the route to the destination device).

[0032] 4 is a diagram showing a first specific example of the configuration of the demultiplexing system 11a. The demultiplexing device 20 in the first specific example includes a demultiplexing unit 21 and a detecting unit 22. The demultiplexing unit 21 may be configured using, for example, a band drop filter (BDF) that separates optical signals by wavelength component, a band pass filter, a WDM filter, or a wavelength multiplexer / demultiplexer. The demultiplexing unit 21 demultiplexes the optical signals input to the optical distribution system 10a. of , the desired signal and the residual signal toA demultiplexing process is performed to separate the wavelengths of the desired demultiplexed signal and the remaining demultiplexed signal. The separated desired demultiplexed signal is input to the cutoff device 30.

[0033] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, instructing the blocking device 30 to block the optical signal (desired separated signal) input to the blocking device 30. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective. That is, the detector 22 may be configured not to reflect the input from the separator 21. Such a log may be recorded together with the detection time of the non-conforming wavelength. By recording the log in this manner, it becomes possible, for example, to respond appropriately to an inquiry when it occurs. Furthermore, such a log may be recorded together with the detected intensity, or together with the detection time and intensity. The same applies hereinafter to the method of using the recorded log.

[0034] When the cutoff device 30 does not cut off the optical signal, it passes the input optical signal. The desired demultiplexed signal that has passed through the cutoff device 30 is output to a path according to its destination. When the cutoff device 30 receives a control signal indicating a cutoff from the detection unit 22 of the demultiplexer 20, it cuts off the input optical signal. In this case, the desired demultiplexed signal is not output to the first side.

[0035] The detector 22 may be configured using, for example, a photodiode (PD) or an avalanche photodiode (APD). The detector 22 detects the signal intensity of the input signal (residual separated signal).

[0036] The blocking device 30 may be configured using, for example: By being configured in this way, the blocking device 30 suppresses signals that are determined to be non-compliant. FXC (Fiber Cross Connect) Optical switch with a specified suppression ratio Optical attenuator with a specified suppression ratio Semiconductor optical amplifiers (e.g., SOAs (Semiconductor Optical Amplifiers) capable of suppressing signals at a specified suppression ratio) - Modulator capable of suppressing at a specified suppression ratio

[0037] Specific examples of the above-mentioned modulator include the following configurations. A device that changes the refractive index by controlling the carrier (conduction electrons and holes) concentration, or the electrorefractive effect by applying an electric field to change the light absorption rate Devices that use the electroabsorption (EA) effect Among modulators that use the ER effect (such as Mach-Zehnder types), those with a wide cutoff wavelength are particularly suitable. Among modulators that use the ER effect, those with little wavelength dependency in refractive index change are particularly suitable from the perspective of widening the cutoff wavelength.

[0038] In the separation system 11a shown in FIG. 4, the presence or absence of a residual separated signal is detected, rather than the ratio of the intensities of the desired separated signal and the residual separated signal. In other words, the presence or absence of a residual signal is detected based on whether the intensity of the residual separated signal exceeds a threshold. Therefore, even if a configuration exists that detects the ratio of the intensities of the desired separated signal and the residual separated signal, the sensitivity can be further improved compared to such a configuration. Furthermore, it is also possible to implement the detection unit 22 using a detector with low sensitivity.

[0039] The demultiplexing system 11a shown in FIG. 4 can output an optical signal (desired demultiplexed signal) that contains a relatively large amount of optical signals of desired wavelengths compared to the residual demultiplexed signal. Furthermore, the demultiplexing system 11a shown in FIG. 4 can block the desired demultiplexed signal (signal input to the blocking device 30) separated by the demultiplexer 21 from the input optical signal when the residual demultiplexed signal obtained from the input optical signal (demultiplexed input signal) is detected with an intensity exceeding a threshold. Unlike the configuration shown in FIG. 5 (described later), the demultiplexing system 11a shown in FIG. 4 continues to input the residual demultiplexed signal of the optical signal input to the demultiplexing system 11a to the detector 22 even while the blocking device 30 is blocking the signal, and the detection process by the detector 22 also continues. Therefore, if the residual demultiplexed signal becomes less than a predetermined optical intensity after blocking, the detector 22 can detect this. In this case, the blocking device 30 may be configured to cancel the blocking. As described above, the deactivation of this cutoff device 30 may be performed, for example, in response to the input of a control signal from the detection unit 22 indicating the deactivation of the cutoff, or in response to the absence of the input of a control signal indicating the cutoff.

[0040] FIG. 5 is a diagram showing a second specific example of the configuration of the demultiplexing system 11a. The demultiplexing device 20 in the second specific example includes a demultiplexing unit 21 and a detecting unit 22. The demultiplexing unit 21 may be configured using, for example, a BDF. In the second specific example, an optical signal input to the demultiplexing system 11a is first input to a blocking device 30. The demultiplexing unit 21 inputs an optical signal that has passed through the blocking device 30, among the optical signals input to the optical distribution system 10a. The demultiplexing unit 21 separates the input optical signal (demultiplexed input signal) into a desired demultiplexed signal and a residual demultiplexed signal by performing a demultiplexing process for wavelength-separating the desired signal from the residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0041] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, instructing it to block the input optical signal. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher.

[0042] When the cutoff device 30 does not cut off the optical signal, it passes the input optical signal. The desired demultiplexed signal that has passed through the cutoff device 30 is input to the demultiplexing unit 21 of the demultiplexer 20. When the cutoff device 30 receives a control signal indicating a cutoff from the detecting unit 22 of the demultiplexer 20, it cuts off the input optical signal. In this case, since no optical signal is input to the demultiplexing unit 21 in the first place, the desired demultiplexed signal is not output to the first side.

[0043] Next, a third specific example of the configuration of the demultiplexing system 11a will be described. In the third specific example, an isolator 23 is provided on the output side of the demultiplexing unit 21 for the residual demultiplexed signal in the configuration of the first specific example. The third specific example will be described in detail below. The demultiplexing device 20 in the third specific example includes a demultiplexing unit 21, a detecting unit 22, and an isolator 23. This configuration prevents an optical signal from being reflected from the detecting unit 22 and returning to the demultiplexing unit 21, or an optical signal input from the port of the demultiplexing unit 21 on the detecting unit 22 side from leaking into the separated desired demultiplexed signal. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 separates the desired demultiplexed signal and the residual demultiplexed signal by performing a demultiplexing process to wavelength-separate the desired signal from the residual demultiplexed signal from the optical signal input to the optical distribution system 10a. The separated desired demultiplexed signal is input to the blocking device 30. The residual demultiplexed signal is input to the isolator 23.

[0044] The isolator 23 passes the optical signal flowing from the separation unit 21 to the detection unit 22 and blocks the optical signal flowing from the detection unit 22 to the separation unit 21. The detection unit 22 receives the residual separated signal via the isolator 23. The detection unit 22 detects the optical intensity of the input residual separated signal. When the detection unit 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30 indicating that the input optical signal (desired separated signal) should be blocked. In this case, the detection unit 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher.

[0045] When the cutoff device 30 does not cut off the optical signal, it passes the input optical signal. The desired demultiplexed signal that has passed through the cutoff device 30 is output to the first side. When the cutoff device 30 receives a control signal indicating cutoff from the detection unit 22 of the demultiplexer 20, it cuts off the input optical signal. In this case, the desired demultiplexed signal is not output to the first side.

[0046] Next, a fourth specific example of the configuration of the separation system 11a will be described. The fourth specific example is a configuration in which an isolator 23 is provided on the output side of the separation unit 21 for the residual separation signal in the configuration of the second specific example. The fourth specific example will be described in detail below. The separation device 20 in the fourth specific example includes a separation unit 21, a detection unit 22, and an isolator 23. The separation unit 21 may be configured using, for example, a BDF. In the fourth specific example, an optical signal input to the separation system 11a is first input to the cut-off device 30. The separation unit 21 inputs the optical signal that has passed through the cut-off device 30 out of the optical signals input to the optical distribution system 10a. The separation unit 21 separates the input optical signal into the desired separation signal and the residual separation signal by performing a separation process to wavelength-separate the desired signal from the residual signal. The separated desired separation signal is output to the first side. The residual separation signal is input to the isolator 23.

[0047] The isolator 23 passes the optical signal flowing from the separation unit 21 to the detection unit 22 and blocks the optical signal flowing from the detection unit 22 to the separation unit 21. The detection unit 22 receives the residual separated signal via the isolator 23. The detection unit 22 detects the optical intensity of the input residual separated signal. When the detection unit 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30 indicating that the input optical signal should be blocked. In this case, the detection unit 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher.

[0048] When the cutoff device 30 does not cut off the optical signal, it passes the input optical signal. The optical signal that has passed through the cutoff device 30 is input to the separation unit 21 of the separation device 20. When the cutoff device 30 receives a control signal indicating a cutoff from the detection unit 22 of the separation device 20, it cuts off the input optical signal. In this case, since no optical signal is input to the separation unit 21 in the first place, the desired demultiplexed signal is not output to the first side.

[0049] FIG. 6 is a diagram illustrating a fifth specific example of the configuration of the demultiplexing system 11a. The demultiplexing device 20 in the fifth specific example includes a plurality of demultiplexing units 21 and a detecting unit 22. The demultiplexing units 21 may be configured using, for example, a BDF. Each demultiplexing unit 21 receives one of the plurality of optical signals input to the optical distribution system 10a. Each demultiplexing unit 21 performs a demultiplexing process to wavelength-separate the desired signal from the residual signal from the input optical signal, thereby separating the desired demultiplexed signal from the residual demultiplexed signal. The separated desired demultiplexed signal is input to the blocking device 30.

[0050] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects a residual separated signal from any of the separators 21 with a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, instructing it to block the input optical signal (desired separated signal). In this case, the detector 22 may record information (log) indicating that the detector 22 has detected a residual separated signal with a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0051] When not blocking, the blocking device 30 passes each input optical signal (desired demultiplexed signal). Each desired demultiplexed signal that has passed through the blocking device 30 is output to the first side. When the blocking device 30 receives a control signal indicating blocking from the detection unit 22 of the demultiplexer 20, it blocks all input optical signals. In this case, none of the desired demultiplexed signals of the multiple optical signals input to the demultiplexing system 11a is output to the first side.

[0052] The interrupter 30 shown in Fig. 6 may be configured in either a configuration in which there is one input and one output (hereinafter referred to as a "first configuration" in the description of the drawings), or a configuration in which multiple inputs are multiplexed and output as a single output (hereinafter referred to as a "second configuration" in the description of the drawings). Each configuration will be described below.

[0053] In the first configuration, the cutoff device 30 may be configured to select cutoff or non-cutoff for each input (i.e., for each separator 21) (hereinafter referred to as "individual cutoff" in the description of the drawings). In the first configuration, the cutoff device 30 may be configured to cut off all inputs (all separators 21) when the detection unit 22 detects a residual separated signal of any one separator 21 at a predetermined light intensity or higher (hereinafter referred to as "total cutoff" in the description of the drawings). The first configuration may be realized, for example, by providing a cutoff device 30 for each separator 21.

[0054] In the second configuration, when blocking optical signals input to the blocking device 30, the blocking device 30 may be configured to block optical signals individually before they are multiplexed, or may be configured to block the optical signal after multiplexing. In the configuration in which optical signals are individually blocked before they are multiplexed, the blocking device 30 may be configured to block individual signals or to block all signals. Note that in the configuration in which optical signals are blocked after multiplexing, the blocking device 30 is configured to block all signals. The second configuration may be realized, for example, by providing a blocking device 30 for each separation unit 21, and providing a multiplexer / demultiplexer or multiplexer / brancher on the output side of each blocking device 30. In this case, the multiplexer / demultiplexer or multiplexer / brancher multiplexes the outputs of each blocking device 30 and outputs the result.

[0055] 6 may be configured as a single-input / multiple-output, multiple-input / single-output, or multiple-input / multiple-output demultiplexers. Such demultiplexers 21 may be configured using, for example, a diffraction grating or an AWG. In this case, the demultiplexers 21 may output the desired demultiplexed signal as a single output to the blocking device 30.

[0056] 7 is a diagram showing a sixth specific example of the configuration of the separation system 11a. The separation system 11a in the sixth specific example includes a separation device 20 and a plurality of cutoff devices 30. The separation device 20 in the sixth specific example includes a plurality of separation units 21 and detection units 22. In the separation system 11a in the sixth specific example, the number of separation units 21 and the number of cutoff devices 30 may be the same.

[0057] In the sixth specific example, an optical signal input to the separation system 11a is first input to a cut-off device 30. One of the multiple optical signals input to the optical distribution system 10a is input to each cut-off device 30. At least one separation unit 21 is connected to the subsequent stage (first side) of each cut-off device 30.

[0058] The demultiplexers 21 may be configured using, for example, a BDF. Of the multiple optical signals input to the optical distribution system 10a, each demultiplexer 21 receives an optical signal that has passed through a cutoff device 30 connected to the upstream (second side) of the device itself. Each demultiplexer 21 performs a demultiplexing process to wavelength-separate the input optical signal into a desired signal and a residual signal, thereby separating the desired demultiplexed signal from the residual demultiplexed signal. The separated desired demultiplexed signal is output to a path on the first side.

[0059] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, indicating that the input optical signal (desired separated signal) should be blocked. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0060] When the cutoff device 30 does not cut off a signal, it passes each input optical signal. Each optical signal that has passed through the cutoff device 30 is output to the demultiplexer 21. When the cutoff device 30 receives a control signal indicating cutting off from the detector 22 of the demultiplexer 20, it cuts off the input optical signal. In this case, among the desired demultiplexed signals of the multiple optical signals input to the demultiplexing system 11a, the desired demultiplexed signals of the optical signals that are cut off by the cutoff device 30 do not reach their destinations. However, the desired demultiplexed signals of the optical signals that are not cut off are transmitted toward their destinations. Note that in the configuration of the sixth specific example, all of the cutoff devices 30 may be configured to cut off optical signals when the detector 22 detects that the residual demultiplexed signal from any one of the demultiplexers 21 has a predetermined optical intensity or higher.

[0061] As described above, in the configuration of the sixth specific example, the passage or blocking of multiple optical signals input to the separation system 11a can be controlled for each individual cutoff device 30. For example, the detection unit 22 may detect a residual demultiplexed signal for the optical signal passing through each cutoff device 30 by turning on the cutoff devices 30 one by one in a predetermined order (by cutting off all of them and then unblocking them one by one). This configuration allows the detection unit 22 to identify which demultiplexer 21 detected a residual demultiplexed signal with a predetermined intensity or higher. In this case, the detection unit 22 may determine to cut off the cutoff device 30 that was turned on at that time only when a residual demultiplexed signal is detected, or may notify the user device that is the source of the optical signal. Alternatively, the detection unit 22 may turn on all of the cutoff devices 30 and simultaneously detect the residual demultiplexed signals for all optical signals.

[0062] 7, a multiplexer / demultiplexer or multiplexer / splitter may be provided on the first side of each separator 21. In this case, the multiplexer / demultiplexer or multiplexer / splitter multiplexes the outputs of the separators 21 and outputs the multiplexed signal. As another configuration example, the multiple separators 21 shown in FIG. 7 may be configured as a single multiple-input, multiple-output separator. Such a separator 21 may be configured using, for example, a diffraction grating or an AWG. In this case, the separator 21 may output the desired separated signal as a single output to the first side.

[0063] FIG. 8 is a diagram showing a seventh specific example of the configuration of the separation system 11a. The separation system 11a in the seventh specific example includes a separation device 20 and multiple circuit breakers 30. In the seventh specific example, multiple circuit breakers 30a are provided in a stage (second side) preceding the separation device 20, and a circuit breaker 30b is provided in a stage (first side) following the separation device 20. The separation device 20 in the seventh specific example includes multiple separation units 21 and a detection unit 22. In the separation system 11a in the seventh specific example, the number of separation units 21 may be the same as the number of circuit breakers 30a provided in the stage (second side) preceding the separation device 20. The circuit breaker 30b in the subsequent stage may be configured using multiple circuit breakers and a multiplexer / demultiplexer or multiplexer / brancher that multiplexes the outputs of each circuit breaker. In this case, the multiple circuit breakers may be connected to corresponding separation units 21. The output of each separation unit 21 is input to the corresponding circuit breaker. The output of each circuit breaker is input to the multiplexer / demultiplexer or multiplexer / brancher. The multiplexer / demultiplexer or multiplexer / splitter multiplexes and outputs the input signals. As another configuration example, the multiple separators 21 shown in FIG. 8 may be configured as a single multiple-input, multiple-output separator. Such a separator 21 may be configured using, for example, a diffraction grating or an AWG. In this case, the separator 21 may output the desired separated signal as a single output to the cutoff device 30b.

[0064] In the seventh specific example, an optical signal input to the separation system 11a is first input to a cut-off device 30a. One of the multiple optical signals input to the optical distribution system 10a is input to each cut-off device 30a. At least one separation unit 21 is connected to the subsequent stage (first side) of each cut-off device 30a.

[0065] The demultiplexers 21 may be configured using, for example, a BDF. Of the multiple optical signals input to the optical distribution system 10a, each demultiplexer 21 receives an optical signal that has passed through a cutoff device 30a connected to the upstream side (second side) of the demultiplexer 21. Each demultiplexer 21 performs a demultiplexing process to wavelength-separate the desired signal from the residual signal from the input optical signal, thereby separating the desired demultiplexed signal from the residual demultiplexed signal. The separated desired demultiplexed signal is output to a cutoff device 30b provided at the downstream side (first side) of the demultiplexer 20.

[0066] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the cutoff device 30a or the cutoff device 30b, instructing the cutoff device 30a or 30b to cut off the input optical signal (desired separated signal). In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0067] When not blocking, the blocking devices 30a and 30b allow the input optical signals to pass. Each optical signal that passes through the blocking device 30a is output to the demultiplexing unit 21. When the blocking device 30a receives a control signal indicating blocking from the detecting unit 22 of the demultiplexing device 20, it blocks the input optical signals. In this case, among the desired demultiplexing signals of the multiple optical signals input to the demultiplexing system 11a, the desired demultiplexing signals of the optical signals blocked by the blocking device 30a are not output to the first side. However, the desired demultiplexing signals of the optical signals that were not blocked are transmitted toward the destination. When the blocking device 30b receives a control signal indicating blocking from the detecting unit 22 of the demultiplexing device 20, it blocks the input optical signals. In this case, none of the desired demultiplexing signals of the multiple optical signals input to the demultiplexing system 11a are output to the first side.

[0068] As described above, in the configuration of the seventh specific example, it is possible to control the passing or blocking of multiple optical signals input to the separation system 11a for each individual cut-off device 30a. For example, the detection unit 22 may detect a residual demultiplexed signal for the optical signal passing through each cut-off device 30a by turning on the cut-off devices 30a one by one in a predetermined order (cutting off all of them and then unblocking them one by one). In this case, the detection unit 22 may determine to block the cut-off device 30a that was turned on at that time only when a residual demultiplexed signal is detected, or may notify the user device that is the sender of the optical signal.

[0069] Alternatively, the detection unit 22 may turn on all the cutoff devices 30a and detect the residual demultiplexed signals of all optical signals collectively. In this case, the detection unit 22 may turn off the cutoff device 30b when a residual demultiplexed signal is detected, thereby cutting off the optical signals collectively. Furthermore, even while the detection unit 22 is turning off the cutoff device 30b, the detection unit 22 may turn on all the cutoff devices 30a. This configuration makes it possible to continuously detect the state of each optical signal (for example, the intensity of the residual demultiplexed signal) while preventing the desired demultiplexed signal of the violating optical signal from flowing to the first side.

[0070] 5 to 8, the specific configurations, actions, and effects of the detection unit 22 and the cutoff device 30 (cutoff device 30a and cutoff device 30b) are the same as those of the separation system 11a shown in FIG. 4. For example, each separation system 11a can be applied to a TFF (Thin Film Filter, dielectric multilayer filter), a FBG (Fiber Bragg Grating), a reflective / transmissive diffraction grating (including an AWG), a ring resonator, an (optical) lattice filter, or an (optical) transversal filter. In other words, any device that extracts one or more wavelengths from a single input light and outputs them as a single output and separates them from the other wavelengths can be applied. Furthermore, as the above-mentioned multiple-input / multiple-output separator, a device can be applied that extracts wavelengths corresponding to the input port from multiple input lights (in the case of PLCs such as AWGs, ring resonators, lattice filters, transversal filters, etc., or PLC coupling) or the input position and angle (in the case of spatially coupled reflective / transmissive diffraction gratings or TFFs that set the selected wavelength by angle) into one output and separates them from other wavelengths.

[0071] 9 to 18 are diagrams showing specific examples of the positional relationship of each device in the first embodiment of the optical distribution system 10 (optical distribution system 10a). In FIGS. 9 to 18, "M" indicated by reference numeral 20 represents the demultiplexer 20, "B" indicated by reference numeral 30 represents the cutoff device 30, "optical distribution SW" indicated by reference numeral 40 represents the optical distribution device 40, and the rectangle indicated by reference numeral 41 represents an additional package. Note that, for ease of explanation, these specific examples show an example in which devices are arranged from the vicinity of the source user device to the central office, but they may be arranged anywhere between the source user device and the destination (receiving) user device. For example, some or all of the devices may be arranged from the central office to the vicinity of the destination user device.

[0072] An add-on package is a device for implementing a function that is additionally added to a PG. For example, an optical signal output from a specific port of the optical distribution device 40 is input to the add-on package 41. The add-on package 41 performs a predetermined process on the input optical signal. The predetermined process may be performed on the electrical signal after converting the optical signal to an electrical signal, or on the optical signal itself. When processing is performed on an electrical signal, the electrical signal is then converted to an optical signal and output from the add-on package 41. The add-on package 41 inputs the optical signal, on which the predetermined process has been performed, to a predetermined port of the optical distribution device 40. The optical distribution device 40 outputs the input optical signal from another port. This configuration enables predetermined processes to be performed on optical signals passing through the optical distribution device 40. The predetermined process performed by the optical distribution device 40 may be, for example, multiplexing, demultiplexing, combining, demultiplexing, branching, or other processes on the optical signal as a node of an all-optical network. The predetermined process performed by the optical distribution device 40 is not limited to the processes described above. 9 to 18, the optical distribution device 40 is installed in a central office. However, the installation location of the optical distribution device 40 does not need to be limited to a central office, and it may be installed, for example, in a building (user building) where user devices are used as an extension. The reference numerals are shown in FIG. 9 and are omitted in FIGS. 10 to 18.

[0073] 9, the separation device 20 and the cut-off device 30 are installed on the second side at a location different from the optical distribution device 40 (a location other than a central office). For example, the separation device 20 and the cut-off device 30 may be installed at the same location as the user device (for example, in a user's premises). For example, either or both of the separation device 20 and the cut-off device 30 may be installed on a telephone pole, in a closure (terminal box), or in a safety box outside the user's premises if they are overhead. For example, the separation device 20 and the cut-off device 30 may be installed underground in a tunnel, manhole, handhole, or MDF room that houses the MDF (Main Distribution Frame) of the user's building.

[0074] 9, an optical signal transmitted from a user device is first input to a demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to a cut-off device 30. An optical distribution device 40 inputs the desired demultiplexed signal that has passed through the cut-off device 30, and outputs the desired signal from a first port.

[0075] The order in which optical signals are input to the demultiplexer 20 and the cut-off device 30 may be reversed. That is, in Fig. 9, as in Fig. 4, the optical signal is first input to the demultiplexer 20, and then the desired demultiplexed signal is input to the cut-off device 30, but as in Fig. 5, the optical signal may be input to the cut-off device 30 first, and if not cut off, the optical signal may then be input to the demultiplexer 20, or as in Fig. 6 or 7, or as in Fig. 8, the optical signals may be input in this order: cut-off device, demultiplexer, cut-off device.

[0076] In FIG. 10, the demultiplexer 20 is installed on the second side at a location different from the optical distribution device 40 (a location other than a central office). For example, the demultiplexer 20 may be installed at the same location as the user device (for example, in a user's premises). In FIG. 10, the optical distribution device 40 functions as the cut-off device 30. In this way, the fact that the optical distribution device 40 functions as the cut-off device 30 is expressed in FIG. 10 by placing a diagram representing the cut-off device 30 on top of a diagram representing the optical distribution device 40.

[0077] In FIG. 10, an optical signal transmitted from a user device is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. In this case, the demultiplexer 20 outputs a control signal to the optical distribution device 40, which is the cut-off device 30. In response to the control signal, the optical distribution device 40 cuts off the desired demultiplexed signal. If the optical distribution device 40 does not cut off the desired demultiplexed signal, it outputs the desired demultiplexed signal from its first port. At this time, the optical distribution device 40 connects the input port and the output port according to the set information, and outputs the desired demultiplexed signal from the output port connected to the input port to which the desired demultiplexed signal was input. The control signal output from the demultiplexer 20 to the cut-off device 30 (optical distribution device 40) may be exchanged via a network that exchanges control signals, such as a DCN (Data Communication Network), or may be exchanged by multiplexing the main signal using AMCC or the like, time division multiplexing, wavelength division multiplexing, or the like.

[0078] 12, 15, 16, 17, and 18, which will be described later, "M" (separator 20) and "B" (interrupter 30) are separated from each other, similar to the configuration shown in Fig. 10. In these cases, communication between the separator 20 and the interrupter 30 is realized in the same manner as the communication shown in Fig. 10.

[0079] Furthermore, in a configuration in which the demultiplexer 20 and the cut-off device 30 are interchanged in the configuration of Figure 10, the main signal is cut off when the cut-off device 30 is in a cut-off state. Therefore, when responding from the cut-off device 30 to the demultiplexer 20, it is not possible to superimpose a control signal on the light of the main signal using AMCC or the like. Therefore, light from a light source other than the main signal must be used, or another transmission method must be used. The same applies to the configuration shown in Figure 15, which will be described later.

[0080] In FIG. 11, the demultiplexer 20 and the cut-off device 30 are implemented in an additional package 41. In FIG. 11, an optical signal transmitted from a user device is first input to the optical distribution device 40. In particular, in the example of FIG. 11, the optical signal is input to the upper left port. The optical distribution device 40 inputs the input optical signal to the additional package 41. The optical signal input to the additional package 41 is input to the cut-off device 30 implemented in the additional package 41. The optical signal that has passed through the cut-off device 30 is input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40.

[0081] The order in which optical signals are input to the isolating device 30 and the demultiplexing device 20 may be reversed. That is, in Fig. 11, the optical signal input to the additional package 41 is first input to the isolating device 30, and if not blocked, is then input to the demultiplexing device 20. Alternatively, the optical signal may be input to the demultiplexing device 20 first, and then the desired demultiplexed signal may be input to the isolating device 30.

[0082] The additional package 41 may also be equipped with functions other than the demultiplexer 20 and the cut-off device 30 (hereinafter referred to as "additional functions"). In this case, the order of processing performed on the optical signal input to the additional package 41 may be, in the example of FIG. 11, first the function of the cut-off device 30, then the demultiplexer 20, and then the additional function; first the function of the cut-off device 30, then the additional function, and then the function of the demultiplexer 20; or first the additional function, then the function of the cut-off device 30, and then the function of the demultiplexer 20. Also, as described above, if the order in which the optical signal is input to the demultiplexer 20 and the cut-off device 30 is reversed from that of FIG. 11, first the function of the demultiplexer 20, then the cut-off device 30, and then the additional function; first the function of the demultiplexer 20, then the additional function, and then the function of the cut-off device 30; or first the additional function, then the function of the demultiplexer 20, and then the function of the cut-off device 30. Note that by configuring the optical signal to be input to the cut-off device 30 before the additional function, it is possible to prevent the additional function of the additional package 41 from being executed on an incompatible optical signal. Furthermore, by configuring the demultiplexer 20 so that the optical signal is input to the demultiplexer 20 before the additional function is input, it becomes possible to output a control signal to the cut-off device 30 indicating that the incompatible optical signal should be cut off at an earlier timing.

[0083] The desired demultiplexed signal output from the additional package 41 having the functions of the demultiplexer 20 and the cut-off device 30 is input to the optical distribution device 40. Then, the optical distribution device 40 outputs the desired demultiplexed signal from a port on the first side.

[0084] 12, the separation device 20 is mounted in an additional package 41. Also, in FIG. 12, the light distribution device 40 functions as the cut-off device 30. In this way, the fact that the light distribution device 40 functions as the cut-off device 30 is expressed in FIG. 12 by placing a diagram representing the cut-off device 30 on top of a diagram representing the light distribution device 40.

[0085] In FIG. 12, an optical signal transmitted from a user device is first input to the optical distribution device 40. In particular, in the example of FIG. 12, it is input to the upper left port. The optical distribution device 40 inputs the input optical signal to the add-on package 41. The optical signal input to the add-on package 41 is input to the demultiplexer 20 implemented in the add-on package 41. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. In this case, the demultiplexer 20 outputs a control signal to the optical distribution device 40, which is the blocking device 30. In response to the control signal, the optical distribution device 40 blocks the desired demultiplexed signal. If the optical distribution device 40 does not block the desired demultiplexed signal, it outputs the desired demultiplexed signal from the first port. The optical distribution device 40 may block the optical signal before input to the additional package, the desired separated signal after output from the additional package, or both. When blocking the optical signal before input to the additional package, the input to the additional package can be blocked, and unnecessary processing in the additional package can be suppressed.

[0086] The additional package 41 may be equipped with a function (additional function) other than the demultiplexer 20. In this case, the order of processing performed on the optical signal input to the additional package 41 may be first the demultiplexer 20 and then the additional function, or first the additional function and then the function of the demultiplexer 20, in the example of Fig. 12. By configuring the optical signal to be input to the demultiplexer 20 before the additional function, it is possible to suppress input of the remaining demultiplexed signal to the additional function, and furthermore, it is possible to output a control signal to the blocking device 30 indicating blocking of the non-compliant optical signal at an earlier timing.

[0087] 13, the demultiplexer 20 and the cut-off device 30 are installed on the second side in the same location (e.g., a central office) as the optical distribution device 40. In FIG. 13, an optical signal transmitted from a user device is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the cut-off device 30. The optical distribution device 40 inputs the desired demultiplexed signal that has passed through the cut-off device 30, and outputs the desired demultiplexed signal from a port on the first side.

[0088] The order in which optical signals are input to the demultiplexer 20 and the cut-off device 30 may be reversed. That is, in Fig. 13, the optical signal is first input to the demultiplexer 20, and then the desired demultiplexed signal is input to the cut-off device 30. However, the optical signal may be input to the cut-off device 30 first, and if it is not cut off, the optical signal may be input to the demultiplexer 20 thereafter.

[0089] In Fig. 14, the demultiplexer 20 and the cut-off device 30 are installed on the first side in the same location (e.g., a central office) as the optical distribution device 40. In Fig. 14, an optical signal transmitted from a user device is first input to the optical distribution device 40. The optical signal output from the port corresponding to the destination in the optical distribution device 40 is then input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the cut-off device 30. The desired demultiplexed signal that has passed through the cut-off device 30 is transmitted to the first side.

[0090] The order in which optical signals are input to the demultiplexer 20 and the cut-off device 30 may be reversed. That is, in Fig. 14, the optical signal is first input to the demultiplexer 20, and then the desired demultiplexed signal is input to the cut-off device 30, but the optical signal may be input to the cut-off device 30 first, and if not cut off, the optical signal may then be input to the demultiplexer 20.

[0091] In FIG. 15, the demultiplexer 20 is installed on the second side at a location different from the optical distribution device 40 (a location other than a central office). For example, the demultiplexer 20 may be installed in the same location as the user equipment (e.g., in a user's premises). The cut-off device 30 is installed on the first side at the same location as the optical distribution device 40 (e.g., a central office). In FIG. 15, an optical signal transmitted from the user equipment is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the first side. The cut-off device 30 inputs the desired demultiplexed signal and cuts it off in accordance with a control signal. The optical distribution device 40 inputs the desired demultiplexed signal that has passed through the cut-off device 30 and outputs the desired demultiplexed signal from a port on the first side.

[0092] The order in which optical signals are input to the demultiplexer 20 and the isolator 30 may be reversed. That is, in Fig. 15, the optical signal is first input to the demultiplexer 20, and then the desired demultiplexed signal is input to the isolator 30, but the optical signal may be input to the isolator 30 first, and if it is not blocked, then the optical signal may be input to the demultiplexer 20. In this case, the mounting positions of the demultiplexer 20 and the isolator 30 are also reversed.

[0093] In Figure 16, the demultiplexer 20 is implemented in the additional package 41. The cut-off device 30 is installed on the second side in the same location (e.g., a central office) as the optical distribution device 40. In Figure 16, the optical signal transmitted from the user device is first input to the cut-off device 30. The optical signal that passes through the cut-off device 30 is input to the optical distribution device 40. In particular, in the example of Figure 16, it is input to the upper left port. The optical distribution device 40 inputs the input optical signal to the additional package 41. The demultiplexer 20 outputs the desired demultiplexed signal to the optical distribution device 40. The optical distribution device 40 inputs the desired demultiplexed signal output from the demultiplexer 20 of the additional package 41 and outputs the desired demultiplexed signal from a port on the first side.

[0094] The order in which optical signals are input to the isolating device 30 and the demultiplexing device 20 may be reversed. That is, in Fig. 16, the optical signal is first input to the isolating device 30, and if not blocked, the optical signal is then input to the demultiplexing device 20. Alternatively, the optical signal may be input to the demultiplexing device 20 first, and then the desired demultiplexed signal may be input to the isolating device 30. In this case, the mounting positions of the demultiplexing device 20 and the isolating device 30 are also reversed.

[0095] In FIG. 17, the demultiplexer 20 is installed on the second side in the same location (e.g., a central office) as the optical distribution device 40. In FIG. 17, the optical distribution device 40 functions as the cut-off device 30. In this way, the fact that the optical distribution device 40 functions as the cut-off device 30 is expressed in FIG. 17 by placing a diagram representing the cut-off device 30 on top of a diagram representing the optical distribution device 40. In FIG. 17, an optical signal transmitted from a user device is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. In this case, the demultiplexer 20 transmits a control signal to the optical distribution device 40. In response to the control signal, the optical distribution device 40 cuts off the desired demultiplexed signal. When the optical distribution device 40 does not cut off the desired demultiplexed signal, it outputs the desired demultiplexed signal from a port on the first side.

[0096] In FIG. 18, the demultiplexer 20 is installed on the first side in the same location (e.g., a central office) as the optical distribution device 40. Also in FIG. 18, the optical distribution device 40 functions as the cut-off device 30. In this way, the fact that the optical distribution device 40 functions as the cut-off device 30 is expressed in FIG. 18 by placing a diagram representing the cut-off device 30 on top of a diagram representing the optical distribution device 40. In FIG. 18, an optical signal transmitted from a user device is first input to the optical distribution device 40. In response to a control signal output from the demultiplexer 20, the optical distribution device 40 cuts off the optical signal. If the optical distribution device 40 does not cut off the optical signal, it outputs the optical signal to the demultiplexer 20. The demultiplexer 20 outputs the desired demultiplexed signal to the first side.

[0097] 11, 12, and 16, when the demultiplexer 20 is implemented in the add-on package 41, the target to be demultiplexed (the wavelength of the optical signal) may be switched over time to determine the residual demultiplexed signal of each optical signal. Such a configuration may be realized, for example, by configuring the input and output of the add-on package 41 as multiple inputs and multiple outputs (for example, n inputs and n outputs: n is an integer of 2 or more) instead of one input and one output, and determining the residual demultiplexed signal of different input optical signals over time.

[0098] 19 to 24 are diagrams showing configuration examples using optical fuses. In FIGS. 19 to 24, the "P" indicated by the reference numeral 91 indicates the optical fuse 91. In FIGS. 19 to 24, the "P" indicated by the reference numeral 91 merely indicates a position where the optical fuse 91 may be provided. In other words, the optical fuse 91 is not necessarily provided at all positions of the "P" indicated by the reference numeral 91. In FIGS. 19 to 24, the positions where the optical fuse 91 may be provided are positions where an optical signal including a desired signal can be transmitted. As examples using optical fuses, examples are shown in FIGS. 19 and 20 using the examples in FIGS. 4 and 5, and examples are shown in FIGS. 21 to 24 in the form corresponding to FIGS. 10, 12, 17, and 18 in which the separation section is integrated with the light distribution section, but they may also be provided at corresponding locations in FIGS. 6, 8, and the later-described corresponding locations in FIGS. 56 to 58, 62 to 63, 72, 73, and 76 to 80, and the corresponding locations in FIGS. 9, 11, and 13 to 16.

[0099] Optical fuse 91 initially allows optical signals to pass, but blocks the subsequent transmission of optical signals when an optical signal of a predetermined intensity or higher is input. The predetermined intensity that serves as the criterion for blocking is so-called high intensity, and is an intensity that could potentially damage equipment such as demultiplexer 20, isolator 30, or optical sorter 40 if an optical signal of that intensity is input.

[0100] The optical fuse 91 may be configured to allow a signal to pass again after being cut off by some process, like an electromagnetic fuse in electricity. The optical fuse 91 may be configured to automatically allow an optical signal to pass when the incompatible high-intensity light disappears. The optical fuse 91 may be realized by combining the cutoff device 30 or another cutoff device (not shown) with a detector (not shown) that detects the input intensity. In this case, the above-mentioned detector and another cutoff device (not shown) may be installed at the position shown as the optical phase 91. In the case of FIG. 19, the above-mentioned detector is installed before the separation unit 21, before the cutoff device 30, or after the cutoff device 30. The detector detects the intensity mismatch and issues an instruction via a path not shown, causing the cutoff device 30 to cut off the signal. Any signal may be used for the instruction. For example, the instruction may be superimposed on the optical signal used by the user signal, or may be communicated using an optical signal with a wavelength different from that used by the user signal. The instruction may also be communicated using a different carrier or line (a different path from that of the main signal) from the optical signal used by the user device. When the detector detects the optical intensity of the optical signal or the desired separated signal at or above a predetermined optical intensity, it outputs a control signal to the blocking device 30 indicating that the optical signal (desired separated signal) input to the blocking device 30 should be blocked. In this case, the detector may record information (log) indicating that the input optical signal (desired separated signal) has been detected at or above a predetermined optical intensity, or may record the detection together with the detected intensity, or may record the time and intensity at which it was detected. By recording the log in this manner, for example, when an inquiry occurs, it becomes possible to appropriately respond to the inquiry. Furthermore, such a log may be recorded together with the detected intensity, or together with the detected time and intensity. The blocking may be performed by completely cutting off the input optical signal (desired demultiplexed signal), or by attenuating the signal to an appropriate intensity and policing the intensity.

[0101] By providing the optical fuse 91 at any of the above positions in the optical distribution system 10, communication control such as policing can be performed with respect to both wavelength and intensity. Intensity-related policing involves attenuating the signal until it reaches an appropriate intensity. Wavelength-related policing involves passing only the desired demultiplexed wavelength in the demultiplexer, or passing the desired demultiplexed wavelength unless the intensity of the remaining demultiplexed wavelengths reaches a predetermined intensity, and then blocking the signal once it reaches the predetermined intensity. Policing with respect to both wavelength and intensity involves attenuating the optical signal (desired demultiplexed signal) until it reaches an appropriate intensity, and then passing only the desired demultiplexed wavelength in the demultiplexer, or passing the desired demultiplexed wavelength unless the intensity of the remaining demultiplexed wavelengths reaches a predetermined intensity, and then blocking the signal once it reaches the predetermined intensity. Furthermore, the optical distribution system 10 can prevent optical surges. It is desirable that the optical fuse 91 used be configured using a device that operates fast enough to prevent optical surges. Each of Figures 19 to 24 will be described below.

[0102] 19, an optical fuse 91 may be provided at any of the following positions: on the second side of the separation unit 21; on the path along which the desired separation signal is output from the separation unit 21, between the separation unit 21 and the cutoff device 30; and on the first side of the cutoff device 30. Unlike the configuration shown in FIG. 20, which will be described later, in the separation system 11a shown in FIG. 19 in which an optical fuse 91 is provided after the separation unit 21, the residual separation signal of the optical signal input to the separation system 11a continues to be input to the detection unit 22 even while the cutoff is being performed by the cutoff device 30 or the optical fuse 91, and the detection process by the detection unit 22 also continues. Therefore, if the residual separation signal becomes less than a predetermined optical intensity after the cutoff, the detection unit 22 can detect this. In this case, the cutoff device 30 and the optical fuse 91 may be configured to release the cutoff.

[0103] In the configuration shown in Figure 20, an optical fuse 91 may be provided at any position on the second side of the cut-off device 30, between the cut-off device 30 and the separation unit 21, or on the first side of the separation unit 21 on the path along which the desired separation signal is output from the separation unit 21.

[0104] In the configuration shown in Fig. 21, the demultiplexer 20 is installed on the second side at a location different from the optical distribution device 40 (a location other than a central office). For example, the demultiplexer 20 may be installed at the same location as the user device (for example, in a user's home). Although the cutoff device 30 is not shown in Fig. 21, the cutoff device 30 may be located anywhere as long as it can function properly. For example, the cutoff device 30 may be located at any of the locations shown in Figs. 9, 10, and 15.

[0105] 21 , the optical fuse 91 may be provided at any of the following positions: on the second side of the demultiplexer 20, at the same location as the demultiplexer 20 (for example, in a user's premises) on the path along which the desired demultiplexed signal is output from the demultiplexer 20, at the same location as the optical distribution device 40 (for example, in a central office) on the path along which the desired demultiplexed signal is output from the demultiplexer 20, inside the optical distribution device 40, or on the first side of the optical distribution device 40. Note that, although it is assumed that the input optical signal passes through the additional package 41, the optical fuse 91 may be provided inside the additional package 41 regardless of the location of the demultiplexer 20, or the optical fuse 91 may be provided between the optical distribution device 40 and the additional package 41.

[0106] In the configuration shown in Fig. 22, the separation device 20 is mounted in an additional package 41. Although the cutoff device 30 is not shown in Fig. 22, the cutoff device 30 may be located anywhere as long as it can function properly. For example, the cutoff device 30 may be located in any of the positions shown in Figs. 11, 12, and 16.

[0107] 22 , the optical fuse 91 may be provided at any of the following positions: on the second side of the optical distribution device 40; on a path within the additional package 41 closer to the user's premises than the separation device 20; on a path within the additional package 41 closer to the first side than the separation device 20; inside the optical distribution device 40; and on the first side of the optical distribution device 40. The optical fuse 91 may also be installed between the optical distribution device 40 and the additional package 41.

[0108] In the configuration shown in Fig. 23, the demultiplexer 20 is installed on the second side in the same location (e.g., in a station building) as the optical distribution device 40. Although the cutoff device 30 is not shown in Fig. 23, the cutoff device 30 may be located anywhere as long as it can function properly. For example, the cutoff device 30 may be located in any of the locations shown in Figs. 13 and 17.

[0109] 23, the optical fuse 91 may be provided at any of the following positions: on the second side of the demultiplexer 20 and in the same location as the demultiplexer 20 (for example, in a central office), between the demultiplexer 20 and the optical distribution device 40 on the path along which the desired demultiplexed signal is output from the demultiplexer 20, inside the optical distribution device 40, or on the first side of the optical distribution device 40. Note that, although it is assumed that the input optical signal passes through the additional package 41, the optical fuse 91 may be provided inside the additional package 41 regardless of the position of the demultiplexer 20, or the optical fuse 91 may be provided between the optical distribution device 40 and the additional package 41.

[0110] In the configuration shown in Fig. 24, the demultiplexer 20 is installed on the first side in the same location (e.g., in a station building) as the optical distribution device 40. Although the cutoff device 30 is not shown in Fig. 24, the cutoff device 30 may be located anywhere as long as it can function properly. For example, the cutoff device 30 may be located in any of the locations shown in Figs. 14 and 18.

[0111] 24, the optical fuse 91 may be provided at any of the following positions: on the second side of the optical distribution device 40 and in the same location as the optical distribution device 40 (for example, in a central office), inside the optical distribution device 40, between the optical distribution device 40 and the demultiplexer 20 on the path along which the optical signal is output, or on the first side of the demultiplexer 20 on the path along which the desired demultiplexed signal is output from the demultiplexer 20. Note that, although it is assumed that the input optical signal passes through the additional package 41, the optical fuse 91 may be provided inside the additional package 41 regardless of the position of the demultiplexer 20, or the optical fuse 91 may be provided between the optical distribution device 40 and the additional package 41.

[0112] 19 to 24, or separately, an optical fuse 91 may be provided between the separation unit 21 and the detection unit 22. With this configuration, it is possible to prevent damage to the detection unit 22. Note that although only the configurations using optical fuses that conform to Figures 4 and 5 are shown, they may also be used in the same manner in Figures 6 to 8 and configurations described below, for example, Figures 56 to 58, Figures 72 to 73, Figures 76 to 79, and 80.

[0113] 25 and 26 are diagrams showing configuration examples using an optical monitor. In FIGS. 25 and 26, the "X" indicated by the reference symbol 92 indicates the optical monitor 92. In FIGS. 25 and 26, the "X" indicated by the reference symbol 92 merely indicates a position where the optical monitor 92 may be provided. In other words, the optical monitor 92 is not necessarily provided at all positions of the "X" indicated by the reference symbol 92. In FIGS. 25 and 26, the positions where the optical monitor 92 may be provided are positions where an optical signal including a desired signal can be transmitted.

[0114] The optical monitor 92 measures the intensity of the optical signal passing through. When the optical monitor 92 detects an optical signal having an intensity equal to or greater than a predetermined intensity, it notifies the cutoff device 30 of the detection result. In this case, the cutoff device 30 may operate to cut off the optical signal. Furthermore, the cutoff device that cuts off the optical signal in accordance with the detection result of the optical monitor 92 may be provided as a separate configuration from the cutoff device 30 of the separation system 11a described with reference to FIGS. 1 to 5, etc., or may be realized in the optical distribution device 40. The instructions from the optical monitor 92 may be transmitted using any signal. For example, the instructions may be superimposed on the optical signal used by the user signal, or may be transmitted using an optical signal with a wavelength different from that used by the user signal. The instructions may also be transmitted using a different carrier or line (a different route from that of the main signal) from the optical signal used by the user device. The optical monitor 92 may record information (log) indicating that the input optical signal (desired separated signal) has been detected at a predetermined optical intensity or above, or may record the detection together with the detected intensity, or may record the detection time and intensity together. The blocking may be performed by completely cutting off the input optical signal (desired demultiplexed signal), or by attenuating the signal to an appropriate intensity and policing the intensity.

[0115] The optical monitor 92, which is provided on the second side of the separator 21, measures the intensity of the optical signal including the desired signal and the residual signal. In this case, a cutoff device that cuts off the optical signal in accordance with the detection result of the optical monitor 92 may be provided on the second side of the optical monitor 92. This configuration makes it possible to prevent damage to the optical monitor 92.

[0116] The optical monitor 92, which is provided on the first side of the demultiplexer 21, measures the intensity of the desired demultiplexed signal. When the optical monitor 92 is provided at any of the above positions, a device may be further provided that attenuates or amplifies the optical signal (desired demultiplexed signal) to a predetermined signal intensity depending on the measurement result of the optical monitor 92. This configuration makes it possible to align the intensity of the output signal (desired demultiplexed signal) with that of the other signals.

[0117] However, by locating the above device at a position closer to the first side than the demultiplexer 21, it becomes possible to appropriately attenuate and amplify the compatible light. Even if the above device is located at a position closer to the second side than the demultiplexer 21, if the input optical signal does not contain light of an incompatible wavelength, appropriate attenuation and amplification can be achieved by processing the signal while taking into account the attenuation of the compatible wavelength in the demultiplexer 21. If the input optical signal contains light of an incompatible wavelength, the intensity of that light will be lower than the desired intensity, but this will not be a problem if the light is blocked. The optical monitor 92 may notify the optical cross-connect located at the first side of the optical monitor 92 of the measurement results. In this case, the intensity between WDM wavelengths may be smoothed in the optical cross-connect, WSS, or ROADM.

[0118] Furthermore, the optical monitor 92 may notify other devices (e.g., optical cross-connect, WSS, ROADM, etc.) on the path of the optical signal of the measurement result. This configuration has the advantage that it is not necessary to measure the optical signal at the device to which the notification is made. For example, the measurement result can be used when adjusting the intensity of a signal in which the measured signal is multiplexed with other signals at the device to which the notification is made. Furthermore, instead of notifying the device of the measurement result, the optical monitor 92 may obtain the value of the measurement result by receiving the measurement result measured by the device. In this case, the optical monitor 92 may be equipped with a function to receive the value (measurement result) measured by the device, instead of a measurement function. Below, each of Figures 25 to 26 will be described.

[0119] In the configuration shown in Figure 25, an optical monitor 92 may be provided at any position, such as on the second side of the separation unit 21, on the path along which the desired separation signal is output from the separation unit 21 and between the separation unit 21 and the cut-off device 30, or on the first side of the cut-off device 30.

[0120] In the configuration shown in Figure 26, an optical monitor 92 may be provided at any position on the second side of the isolation device 30, between the isolation device 30 and the separation unit 21, or on the first side of the separation unit 21 on the path along which the desired separation signal is output from the separation unit 21.

[0121] The position where the optical monitor 92 is provided is not limited to those shown in Figures 25 and 26. For example, the optical monitor 92 may be provided at the position where the optical fuse 91 is provided in the configurations shown in Figures 21 to 24. As with the configurations including an optical fuse, the optical monitor 92 may be provided at the corresponding positions in Figures 6, 8, Figures 56 to 58, 62 to 63, 72, 73, 76 to 80, and the corresponding positions in Figures 9, 11, 13, 14, 15, and 16, which will be described later.

[0122] In a configuration including an optical monitor 92, the detector 22 may correct the optical intensity of the demultiplexed input signal or the desired demultiplexed signal based on the measurement results of the optical monitor 92. If the wavelength demultiplexing characteristics of the demultiplexer 21 are not ideal, the separation of the desired signal and the residual signal will be incomplete. That is, the desired wavelength component will leak into the residual demultiplexed signal, and the residual wavelength component will leak into the desired demultiplexed signal. Therefore, even if there are no residual wavelength components that are wavelength-incompatible, if the intensity of the desired signal is high, the leakage of the desired wavelength component may cause the detected intensity of the residual demultiplexed signal to become non-zero, potentially resulting in an erroneous detection of wavelength incompatibility. By correcting the detected intensity of the residual demultiplexed signal in accordance with this leakage of the desired wavelength component into the residual demultiplexed signal, it is possible to reduce the risk of erroneous detection of wavelength incompatibility.

[0123] When the intensity of the optical signal (desired demultiplexed signal) after being demultiplexed by the demultiplexer 21 is obtained by the optical monitor 92, the detector 22 may perform the following process. First, when measuring the intensity of the optical signal, the optical monitor 92 branches the optical signal for measurement at a predetermined branching ratio. The optical monitor 92 measures the intensity of the branched optical signal for measurement and notifies the detector 22 of the measured value. The detector 22 then discounts the measured value back to the intensity of the optical signal before being measured by the optical monitor 92, based on the loss when the optical signal is branched and the branching ratio.

[0124] The detector 22 calculates the optical intensity of the matching wavelength component leaked into the residual separated signal separated by the detector 21 based on the suppression ratio in the separation process in the detector 21 and the optical intensity of the optical signal input to the detector 22 itself. The detector 22 then subtracts the calculated optical intensity from the intensity of the residual separated signal separated by the detector 21, thereby enabling more accurate calculation of the optical intensity of the residual signal. The detector 22 determines the intensity of the residual signal based on the optical intensity thus obtained. Note that while only the configurations conforming to FIGS. 4 and 5 are shown using an optical monitor, it may also be used in FIGS. 6 to 8 and configurations described below, such as FIGS. 56 to 58, 72 to 73, and 76 to 79. Here, in the configurations of Figures 56 to 58, Figures 62 to 63, and Figures 71 to 79 described below, the arrangement of the relevant functions may be the arrangement shown in Figures 9 to 18, or similarly, the optical fuses and optical monitors shown in Figures 19 to 26 may be arranged, or other appropriate combinations may be used.

[0125] Next, a specific example of the configuration of the separator 21 will be described. For example, the specific example described below may be applied to each separator 21 shown in FIGS. 4 to 8. In this case, the blocking device 30 is not shown in the following description in order to merely describe the specific example of the configuration of the separator 21. However, the blocking device 30 shown in FIGS. 4 to 8 may block signals related to the separator 21 (such as the separated input signal and the desired separated signal). When the specific example of the separator 21 described below is applied to the separator 21 shown in FIGS. 6 to 8, each separator 21 separates signals at wavelengths corresponding to different desired wavelengths and residual wavelengths corresponding to multiple different inputs. Furthermore, in the following description, one or more elements such as filters will be described as elements constituting the separator 21. In this case, each element (e.g., an FBG 212) performs a separation process, and the signal input to the element is separated into a desired separated signal and a residual separated signal. When the separator 21 is composed of multiple elements, the desired separated signal or the residual separated signal separated by the preceding element is input to the subsequent element. Furthermore, when the separating unit 21 is configured with a plurality of elements, the corresponding desired wavelengths (suitable wavelengths) may differ depending on the elements. In this case, the separating process is performed in accordance with the corresponding desired wavelengths in each element.

[0126] 19, 20, 25, 26, and FIGS. 72, 73, 76, and 77, which will be described later. With regard to FIGS. 19 and 20, even in a configuration in which an optical monitor 92(X) is provided instead of an optical fuse 91(P), the specific examples in the following description may be applied to the respective separation units 21. Furthermore, both the optical fuse 91(P) and the optical monitor 92(X) may be provided. In this case, the specific examples in the following description may also be applied to the respective separation units 21.

[0127] In this case, the following description will be omitted in order to merely describe specific examples of the configuration of the separator 21, but a notification signal may be output from the detector 22, or a detection result may be output, based on the residual separated signal output from the separator 21 in each of the following specific examples. Similarly, the residual separated signal output from the separator 21 in each of the following specific examples may be discarded by the discarder 24. A multiple-input, multiple-output separator such as those described in FIGS. 6, 7, and 8 may also be applied.

[0128] Figure 6 shows a multi-input, single-output separation system (separation device (separation section + detection section) + circuit breaker), which includes a multi-input, multi-output separation device 20 (separation section + detection section) and multiple single-input separation sections 21. In Figure 6, the outputs of multiple separation sections 21 are input to a multi-input, single-output circuit breaker 30. The multi-input, single-output circuit breaker 30 may be configured by multiplexing the outputs of single-input, single-output circuit breakers for the number of ports using a multiplexer / branch, or by multiplexing ports using a multiplexer / branch and inputting the output to a single-input, single-output circuit breaker. The circuit breaker 30 in Figure 6 can also be configured from a set of single-input, single-output circuit breakers to form a multi-input, multi-output separation system, as in Figure 7.

[0129] FIG. 7 shows a multiple-input, multiple-output separation system 11a (separation device (separation section + detection section) + interruption device), which includes a multiple-input, multiple-output separation device 20 (separation section + detection section), which includes a plurality of single-input separation sections 21. In FIG. 7, the outputs of the plurality of separation sections 21 can be multiplexed using a multiplexer / brancher to form a multiple-input, single-output separation system similar to FIG. 6.

[0130] For example, in the configuration shown in Fig. 73 or the configuration shown in Fig. 77, which will be described later, a multiple-input multiple-output demultiplexer may be applied instead of providing multiple demultiplexers 21. In this case, the multiple-input multiple-output demultiplexer may be configured to receive inputs from multiple ports and output a desired demultiplexed signal from one port (multiple-port input single-port output).

[0131] In the following explanation, different reference numerals are used to distinguish between components in the same drawing, but even if the reference numerals are the same in different drawings, the components do not operate in exactly the same way. For example, the FBG 212a in Fig. 28 and the FBG 212a in Fig. 29 are both FBGs, but they are used in different ways and therefore operate differently.

[0132] [Example 1: FBG] FIG. 27 is a diagram showing a first configuration example in which the separation unit 21 is configured using an FBG (Fiber Bragg Grating). An FBG is configured by inscribing a diffraction grating into an optical fiber. When light is incident on the FBG, only light with a specific wavelength component according to the spacing of the diffraction grating is reflected, and light with other wavelength components passes through. By utilizing such characteristics, the separation unit 21 can be configured using an FBG.

[0133] The separation unit 21 includes a circulator 211 and an FBG 212. The circulator 211 inputs an optical signal input from the second side to the FBG 212. The circulator 211 outputs an optical signal input from the FBG 212 to the first side. The circulator 211 may be configured using, for example, an optical multiplexer / demultiplexer. When the circulator 211 is configured using a 2×2 optical multiplexer / demultiplexer, two ports on one side function as an input port and an output port, one of two ports on the other side is connected to the FBG 212, and the other port is configured as a non-reflective termination. The circulator 211 may also be configured using a 2×1 optical multiplexer / demultiplexer so as not to have an open end. In this case, two ports on one side function as an input port and an output port, and one port on the other side is connected to the FBG 212. The FBG 212 reflects an optical signal of a desired wavelength and transmits optical signals of the remaining wavelengths. Through such reflection and transmission, the desired separated signal and the remaining separated signal are separated from the separated input signal.

[0134] FIG. 28 is a diagram showing a second configuration example in which the separation unit 21 is configured using FBGs. In the example shown in FIG. 28, the separation unit 21 includes a circulator 211 and a plurality of FBGs 212 (for example, two FBGs (FBG 212a and FBG 212b)). The circulator 211 inputs the optical signal input from the second side to the FBG 212a. The circulator 211 inputs the optical signal input from the FBG 212a to the FBG 212b. The circulator 211 outputs the optical signal input from the FBG 212b to the first side. Note that although FIG. 28 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0135] The FBGs 212a and 212b reflect optical signals of desired wavelengths and transmit optical signals of remaining wavelengths. With this configuration, it is possible for the FBG 212b to further remove optical signals of remaining wavelengths that could not be completely removed by the FBG 212a. The detection unit 22 may receive the output of either the FBG 212a or the FBG 212b, or both. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0136] For example, to more accurately detect whether a residual signal is mixed into the optical signal input to the optical distribution system 10a, it is desirable to use the output of the FBG 212a. To estimate the optical intensity of a residual signal that cannot be removed by the separation unit 21 (a residual signal that mixes into the desired separated signal), it is desirable to use the output of the FBG 212b. For example, if the reflectance of the residual signal is β and the loss of the circulator 211 is zero, if an optical intensity of B×(1−β) is detected at the output of the FBG 212a, this means that a residual signal of B×β^2 has mixed into the desired separated signal output to the first side. When the same level of mixing occurs, an optical intensity of B×β×(1−β) is detected at the FBG 212b, which indicates that the intensity is reduced by β times. This phenomenon also applies to the following embodiments. The circulator 211 may be configured using an optical multiplexer / demultiplexer, as in the first configuration example.

[0137] Fig. 29 is a diagram showing a third configuration example in which the separator 21 is configured using an FBG. In Fig. 29, a Mach-Zehnder interferometer using an FBG (hereinafter referred to as a Mach-Zehnder type) is applied. The separator 21 includes a plurality of directional couplers (optical multiplexers / demultiplexers) 213 (213a and 213b) and a plurality of FBGs 212 (FBGs 212a and FBGs 212b).

[0138] In the case of a Mach-Zehnder interferometer, a pair of FBGs 212 is installed in each arm of the Mach-Zehnder interferometer. If the distances from the input directional coupler constituting the Mach-Zehnder interferometer to the two gratings are the same, their reflected light will merge and interfere, and then be output from the lower-left port. Therefore, it is necessary not only to match the characteristics of the two gratings, but also to match the distance from the directional coupler to the grating with an accuracy of at least one wavelength or less, for example, one-tenth of the wavelength or less. Therefore, after forming the grating, a method is required to adjust the optical length by so-called trimming, which involves irradiating the area between the grating and the directional coupler with ultraviolet light to change the refractive index.

[0139] The directional coupler 213a receives an optical signal from its upper left port and outputs the desired separated signals reflected by the FBGs 212a and 212b from its lower left port. The residual separated signals that have passed through the FBGs 212a and 212b are input to the upper left and lower left ports of the directional coupler 213b, respectively. The directional coupler 213b outputs the residual separated signals from its upper right and lower right ports. Note that the directional coupler 213b may output the residual separated signals to the detector 22 from only one of its two ports (the upper right and lower right ports in FIG. 29). In this case, the other port may be configured as a non-reflection termination, for example, or may be connected to an isolator.

[0140] FIG. 30 is a diagram showing a fourth configuration example in which the separator 21 is configured using FBGs. In the example shown in FIG. 30, the separator 21 includes multiple directional couplers 213 (213a to 213d) and multiple FBGs 212 (212a to 212d). The directional coupler 213a receives an optical signal from its upper left port and outputs the desired separated signals reflected by the FBGs 212a and 212b from its lower left port. The directional coupler 213c receives the desired separated signals output from the lower left port of the directional coupler 213a from its upper left port. The directional coupler 213c outputs the desired separated signals reflected by the FBGs 212c and 212d from its lower left port. The directional couplers 213b and 213d output the residual separated signals from their upper right and lower right ports, respectively. The directional coupler 213b may output the residual separated signal to the detector 22 from only one of the two ports (the upper right and lower right ports in FIG. 30). In this case, the other port may be configured as a non-reflective termination, or may be connected to an isolator. This configuration also applies to the directional coupler 213d. Although FIG. 30 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0141] With this configuration, it is possible to further remove optical signals of residual wavelengths that could not be completely removed by the FBGs 212a and 212b in the FBGs 212c and 212d. The detection unit 22 may receive the output of only one of the directional couplers 213b and 213d, or may receive both. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0142] 27 to 30, assuming that each grating can only separate one wavelength, it is necessary to connect gratings with different reflection wavelengths in multiple stages to demultiplex an optical signal in which light of multiple different wavelengths is multiplexed (for example, optical signals such as DWDM or CWDM). When the number of wavelengths is large, as in the case of a dielectric multilayer filter, miniaturization, cost reduction, and improvement of mass productivity become issues. A design in which gratings with different reflection wavelengths are connected in multiple stages can be performed on silica glass waveguides or semiconductor optical waveguides, rather than as a combination of individual components, and the design can be integrated into a monolithic PLC or hybrid PLC.

[0143] 31 to 34, which will be described below, use desired signals of multiple wavelengths. For simplicity, the following description assumes that a first desired signal having a first desired wavelength λi and a second desired signal having a second desired wavelength λj are separated from the residual signal.

[0144] In the configurations shown in Figures 27 to 30, if each grating separates only one wavelength, a desired signal of one wavelength is used. However, in the configurations shown in Figures 27 to 30, if multiple wavelengths are reflected by apodization or the like, it is possible to accommodate desired signals of multiple wavelengths by overlaying gratings corresponding to multiple wavelengths without cascading them. When accommodating desired signals of multiple wavelengths using gratings that separate only one wavelength per grating, use Figures 31 to 34.

[0145] 31 is a diagram showing a fifth configuration example in which the separating unit 21 is configured using FBGs. The separating unit 21 includes a circulator 211, FBGs 212i, and FBGs 212j. The circulator 211 inputs the optical signal input from the second side to the FBGs 212i and 212j. The circulator 211 outputs the optical signals input from the FBGs 212i and 212j to the first side, respectively. The FBG 212i reflects the optical signal of the first desired wavelength (first desired signal) and transmits optical signals of other wavelengths (second desired wavelength and remaining wavelength). The FBG 212j reflects the optical signal of the second desired wavelength (second desired signal) and transmits optical signals of other wavelengths (the remaining wavelength and the first desired wavelength that was not reflected by the preceding FBG 212i and transmitted). Through such reflection and transmission, the desired separated signal and the remaining separated signal are separated from the separated input signal. In the configuration of FIG. 31, the circulator 211 may be configured using an optical multiplexer / demultiplexer, similar to the configuration described with reference to FIG.

[0146] Fig. 32 is a diagram showing a sixth configuration example in which the separator 21 is configured using FBGs. In the example shown in Fig. 32, the separator 21 includes a circulator 211 and a plurality of FBGs 212 (FBGs 212ai, FBGs 212aj, FBGs 212bi, and FBGs 212bj). The circulator 211 inputs the optical signal input from the second side to the FBG 212ai. The circulator 211 inputs the optical signal input from the FBG 212ai to the FBG 212bi. The circulator 211 outputs the optical signal input from the FBG 212bi to the first side. Note that while Fig. 32 shows a two-stage cascade configuration, a three or more stage cascade configuration may also be used. Note that a plurality of stages is desirable from the viewpoint of aligning the propagation delay.

[0147] The FBGs 212ai and 212bi reflect an optical signal of a first desired wavelength (first desired signal) out of the optical signals input from the circulator 211 side, and transmit optical signals of other wavelengths (second desired wavelength and remaining wavelengths). The FBGs 212aj and 212bj reflect an optical signal of a second desired wavelength (second desired signal) out of the optical signals input from the FBGs 212ai and 212bi, respectively, and transmit optical signals of other wavelengths (the remaining wavelengths and the first desired wavelength that was transmitted without being reflected by the preceding FBG 212ai or FBG 212bi). The FBGs 212ai and 212bi transmit the light input from the FBGs 212aj and 212bj, respectively, to the circulator 211.

[0148] With this configuration, it is possible for the FBGs 212bi and 212bj to further remove optical signals of residual wavelengths that could not be completely removed by the FBGs 212ai and 212aj. Only one output of the FBGs 212aj and 212bj, or both, may be input to the detection unit 22. When only one output of the FBGs 212aj and 212bj is input to the detection unit 22, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0149] Furthermore, the propagation delay may be set to the same value for optical signals of multiple suitable wavelengths reflected by the FBG 212. For example, assume that the propagation delay (the product of the refractive index and the round-trip distance) from the circulator 211 to reflection on the grating is 100 for the FBGs 212ai and 212bi, and 200 for the FBGs 212aj and 212bj. The total propagation delay for the reflected wavelength of the FBG 212ai is 200, and the total propagation delay for the reflected wavelength of the FBG 212aj is 400. Therefore, under the above assumption, the propagation delay will differ depending on the wavelength.

[0150] Therefore, for example, by making the reflection wavelengths of the FBGs 212ai and 212bj the same, and the reflection wavelengths of the FBGs 212bi and 212aj the same, and by making the sum of the propagation delays when reflected by the FBGs 212ai and 212bj equal to the sum of the propagation delays when reflected by the FBGs 212bi and 212aj, the propagation delays of both wavelengths can be made equal. To make the sum of the propagation delays equal, for example, the propagation delays of the FBGs 212ai and 212bi, and the FBGs 212aj and 212bj may be made equal. Note that while the above description uses two different wavelengths, even if optical signals of three or more different wavelengths are used, it is sufficient to make the sum of the propagation delays of multiple compatible wavelengths reflected by the FBG 212 equal. Note that the circulator 211 may be configured using an optical multiplexer / demultiplexer, as in the fifth configuration example. In this case, the output port of the previous stage of the 2×2 optical multiplexer / splitter and the input port of the next stage are connected in cascade.

[0151] Fig. 33 is a diagram showing a seventh configuration example in which the separator 21 is configured using an FBG. In Fig. 33, a Mach-Zehnder type FBG is applied as the FBG. The separator 21 includes a plurality of directional couplers 213 (213a and 213b) and a plurality of FBGs 212 (FBG 212ai, FBG 212aj, FBG 212bi, and FBG 212bj).

[0152] The directional coupler 213a receives an optical signal from its upper left port and outputs a desired separated signal of the first desired signal and a desired separated signal of the second desired signal reflected by the FBGs 212ai, 212aj, 212bi, and 212bj from its lower left port. The residual separated signals transmitted through the FBGs 212ai, 212aj, 212bi, and 212bj are input to the upper left and lower left ports of the directional coupler 213b. The directional coupler 213b outputs the residual separated signal from its upper right port to the detector 22. In this case, the remaining port of the directional coupler 213b (the lower right port) may be configured as a reflection-free termination or may be connected to an isolator. Alternatively, the directional coupler 213b may output the residual separated signals from two ports (the upper right port and the lower right port) to the detector 22.

[0153] Furthermore, the propagation delays of the optical signals of the multiple suitable wavelengths reflected by the FBG 212 are adjusted to the same value. For example, the reflection wavelengths of FBG 212ai and FBG 212bi are adjusted to the same value, and the reflection wavelengths of 212bj and 212aj are adjusted to the same value. Note that although the above explanation deals with two different wavelengths, even when optical signals of three or more different wavelengths are used, the propagation delays of the multiple suitable wavelengths reflected by the FBG 212 are adjusted to the same value in both arms.

[0154] FIG. 34 is a diagram showing an eighth configuration example in which the separator 21 is configured using FBGs. In the example shown in FIG. 34, a Mach-Zehnder type FBG is used as the FBG. The separator 21 includes a plurality of directional couplers 213 (213a to 213d) and a plurality of FBGs 212 (212ai to 212di, 212aj to 212dj). The directional coupler 213a receives an optical signal from its upper left port, and outputs a desired demultiplexed signal of the first desired signal and a desired demultiplexed signal of the second desired signal reflected by the FBGs 212ai, 212aj, 212bi, and 212bj from its lower left port. Note that while FIG. 34 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used. Note that a plurality of stages is desirable from the viewpoint of aligning the propagation delay.

[0155] The directional coupler 213c receives the desired separated signal of the first desired signal and the desired separated signal of the second desired signal output from the lower left port of the directional coupler 213a, via its upper left port. The directional coupler 213c outputs the desired separated signal of the first desired signal and the desired separated signal of the second desired signal reflected by the FBGs 212ci, 212cj, 212di, and 212dj, respectively, via its lower left port. The directional couplers 213b and 213d each output the residual separated signal from their upper right ports to the detector 22. In this case, the remaining port (lower right port) of the directional coupler 213d may be configured as a reflection-free termination or may be connected to an isolator. Alternatively, the directional coupler 213d may output the residual separated signal from two ports (the upper right port and the lower right port) to the detector 22.

[0156] Furthermore, with regard to the FBG 212ci, FBG 212cj, FBG 212di, and FBG 212dj, the propagation delays of optical signals of multiple suitable wavelengths reflected by the FBG 212 may be made to be the same value. For example, the propagation delays of both wavelengths can be made uniform by making the reflection wavelengths of the FBGs 212ai, 212bi, 212cj, and 212dj the same, and making the reflection wavelengths of the FBGs 212aj, 212bj, 212di, and 212ci the same, and making the sum of the propagation delays upon reflection by the FBGs 212ai and 212bi and the propagation delays upon reflection by the FBGs 212cj and 212dj equal to the sum of the propagation delays upon reflection by the FBGs 212aj and 212bj and the propagation delays upon reflection by the FBGs 212di and 212ci equal. Although the above description deals with two different wavelengths, even if optical signals of three or more different wavelengths are used, it is sufficient to adjust the sum of the propagation delays of multiple suitable wavelengths reflected by the FBG 212 in the same manner.

[0157] With this configuration, optical signals of the second desired wavelength and the remaining wavelengths that could not be completely removed by the FBGs 212ai and 212bi can be further removed by the FBGs 212ci and 212di. Similarly, optical signals of the remaining wavelengths that could not be completely removed by the FBGs 212aj and 212bj can be further removed by the FBGs 212cj and 212dj. The detector 22 may receive the output of either the directional coupler 213b or the directional coupler 213d, or both. When the detector 22 receives the output of only one of the directional couplers 213b and 213d, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separator 21 and the detector 22.

[0158] Furthermore, the propagation delays of optical signals of multiple suitable wavelengths reflected by the FBG 212 may be aligned to the same value. (FBGs 212ai and FBG 212bi), (FBGs 212aj and FBG 212bj), (FBGs 212ci and FBG 212di), and (FBGs 212cj and FBG 212dj), which are arranged at equal distances from the multiplexer / brancher of each arm, each have the same reflected wavelength. As with the explanation in FIG. 32, to align the propagation delays for each wavelength, the reflected wavelengths of (FBGs 212ai and FBG 212bi), (FBGs 212cj and FBG 212dj), (FBGs 212aj and FBG 212bj), and (FBGs 212ci and FBG 212di) are set to the same wavelength, and the sum of the propagation delays of FBGs 212ai and FBG 212cj is made equal to the sum of the propagation delays of FBGs 212aj and FBG 212ci. For example, the propagation distances of the FBGs 212ai, 212bi, 212ci, and 212di may be set to be equal, and the propagation distances of the FBGs 212aj, 212bj, 212cj, and 212dj may be set to be equal.

[0159] The following configuration is also preferable: At least the propagation distances from the input-side optical multiplexer / demultiplexer between FBG212ai and FBG212bi, between FBG212aj and FBG212bj, between FBG212ci and FBG212di, and between FBG212cj and FBG212dj are equal to each other and the wavelengths reflected are equal to each other. Furthermore, in order to align the propagation delay times for each wavelength, it is further preferable that FBG212ai, FBG212bi, FBG212cj, and FBG212dj, FBG212aj, FBG212bj, FBG212ci, and FBG212di have the same wavelength, and the propagation delays of the wavelengths reflected by FBG212ai and FBG212cj are equal to the propagation delays of the wavelengths reflected by FBG212aj and FBG212ci.

[0160] [Example 2: TFF] First, we will explain about multilayer filters. Multilayer filters are usually dielectric multilayer filters, and here we will explain them as TFFs. We will explain about TFFs (Thin Film Filters).

[0161] In the following explanation, a dielectric filter is used as the TFF. A dielectric filter is a wavelength filter that utilizes interference phenomena in a multilayer structure of dielectric thin films. Dielectric filters are fabricated using vacuum deposition techniques such as electron beam evaporation and reactive sputtering. Typical dielectric materials used in dielectric filters include Al2O3, HfO2, MgF2, Nb2O5, Si, SiO2, Ta2O5, TiO2, Y2O3, and ZrO2. The refractive index of a dielectric material depends on the material and ranges from 1.38 (MgF2) to 3.5 (Si). Dielectrics are used in wavelength ranges where absorption is negligible. A multilayer film is composed of several (usually two) dielectric materials with different refractive indices. The thickness of each layer is approximately the wavelength of light or less (0.05 to several microns). A multilayer film can have more than 100 layers. Light is incident perpendicularly or obliquely on the film surface; some of it is reflected and the rest is transmitted. An advantage of TFF is that it can be designed to have high transmittance and reflectance (95% or higher) or specific values ​​(1 to 99%).

[0162] For example, in a BPF, light of wavelengths outside the transmission band is reflected (or absorbed). A structure in which two parallel mirrors face each other is called a resonator (cavity). A dielectric BPF has a structure in which a dielectric spacer layer (λ / 2) is sandwiched between two highly reflective multilayer mirrors (λ / 4 layers), a so-called Fabry-Perot resonator structure. Light incident on the BPF is split into multiple beams through repeated multiple reflections in the cavity, and light is transmitted at specific wavelengths where the phases of the multiple beams are constructively coupled. By stacking multilayer structures in multiple stages with λ / 4 coupling layers between them, the spectral shape can be made closer to a box shape (multi-cavity BPF). The transmission wavelength of a BPF depends on the optical film thickness of the spacer layer. For example, by using a material with a large refractive index temperature coefficient (e.g., Si) for the spacer layer, it is possible to control the transmission wavelength with temperature.

[0163] In addition, the structure is made by alternately depositing dielectric thin films with high and low refractive indices, each with a thickness of λ / 4, and the thickness of each pair (one period) of high and low refractive index layers is λ / 2, so the reflected light from each layer interface is added in phase, resulting in a mirror. When this λ / 4 multilayer mirror is placed opposite each other with a spacer layer with a thickness of λ / 2 between them, it forms a Fabry-Perot structure, and only the resonant wavelength is transmitted.

[0164] By changing the optical film thickness of the dielectric spacer layer (λ / 2), the transmission wavelength of the TFF can be adjusted to any value. For example, as described above, if a material with a large refractive index temperature coefficient (e.g., Si) is used for the spacer layer, the transmission wavelength can be controlled by temperature. Alternatively, a spacer layer with a different thickness may be formed perpendicular to the optical path, and the average film thickness may be changed by sliding the spacer layer horizontally along the thickness axis. Alternatively, the optical film on the optical path may be effectively changed by tilting the incident angle relative to the optical path. In the following description, the TFF reflects an optical signal perpendicularly, and the reflected light is input to the detector 22 by a circulator. The TFF can adjust the reflected and transmitted wavelengths according to the angles of incidence and emission. For example, when different input light beams from different angles are converted to wavelengths appropriate for each angle, the TFF can be used as a multiple-input, single-output separator 21, similar to a diffraction grating.

[0165] 35 is a diagram showing a first configuration example in which the separating unit 21 is configured using a TFF. The separating unit 21 includes a circulator 211 and a TFF 214. The circulator 211 inputs an optical signal input from the second side to the TFF 214. The circulator 211 inputs an optical signal input from the TFF 214 to the detecting unit 22. The configuration of the circulator 211 is as described above.

[0166] Note that, for example, the light traveling direction rotates in the opposite direction as viewed from the page between the circulator 211 in Fig. 27 and the circulator 211 in Fig. 35. When the element in the separation unit 21 is configured to reflect light of a suitable wavelength, such as the FBG 212, or when the element is configured to transmit light of a suitable wavelength, such as the TFF 214, the light traveling direction in the circulator 211 rotates in the opposite direction as described above.

[0167] The TFF 214 transmits an optical signal of a desired wavelength and reflects an optical signal of a remaining wavelength. The optical signal reflected by the TFF 214 (the remaining demultiplexed signal) is input to the detection unit 22 via the circulator 211. Through such reflection and transmission, the desired demultiplexed signal and the remaining demultiplexed signal are separated from the demultiplexed input signal. Note that even in the configuration of FIG. 35 that transmits the desired wavelength, the circulator 211 may be configured using an optical multiplexer / demultiplexer, as in the configuration of FIG. 27 that reflects the desired wavelength. This also applies to other configurations.

[0168] Fig. 36 is a diagram showing a second configuration example in which the separator 21 is configured using TFFs. In the example shown in Fig. 36, the separator 21 includes a plurality of circulators 211 (for example, circulator 211a and circulator 211b) and a plurality of TFFs 214 (for example, TFF 214a and TFF 214b). The circulator 211a inputs the optical signal input from the second side to the TFF 214a. The circulator 211a inputs the optical signal input from the TFF 214a to the detector 22. Note that although Fig. 36 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0169] Of the optical signals input from the circulator 211a, the TFF 214a passes the desired demultiplexed signal to the circulator 211b and reflects the residual demultiplexed signal to input to the circulator 211a. The circulator 211b inputs the optical signal input from the TFF 214a (the residual demultiplexed signal) to the TFF 214b. In this way, the TFF 214a transmits light of a compatible wavelength, so that mainly the compatible wavelength component travels from the TFF 214a to the TFF 214b. The circulator 211b inputs the optical signal reflected and input from the TFF 214b (the residual demultiplexed signal) to the detector 22. Of the optical signals input from the circulator 211b, the TFF 214b passes the desired demultiplexed signal to the transmission path and reflects the residual demultiplexed signal to input to the circulator 211b.

[0170] With this configuration, it is possible for the TFF 214b to further remove optical signals of residual wavelengths that could not be completely removed by the TFF 214a. The output of either the circulator 211a or the circulator 211b may be input to the detecting unit 22, or both may be input. When the output of only one of the circulators 211a or 211b is input to the detecting unit 22, the other output may be configured as a reflection-free termination or may be connected to an isolator.

[0171] An isolator 23 may be provided between the separator 21 and the detector 22. The circulator 211b is not necessarily provided. In this case, the residual separated signal separated in the TFF 214b is not input to the detector 22, which may slightly reduce the accuracy of processing in the detector 22, but it is possible to remove the residual component of the residual signal from the desired separated signal. The incompatible wavelength components reflected in the TFF 214b return to the TFF 214a. However, if these incompatible wavelength components are reflected by the TFF 214a or the circulator 211a, the incompatible wavelength components will be input again to the path of the compatible wavelength components (the path to the first side). To prevent this, an isolator may be provided somewhere between the TFF 214a and the TFF 214b, for example.

[0172] 37 to 39, which will be described below, use desired signals of multiple wavelengths. For simplicity, the following description assumes that a first desired signal having a first desired wavelength λi and a second desired signal having a second desired wavelength λj are separated from the residual signal.

[0173] FIG. 37 is a diagram showing a third configuration example in which the demultiplexing unit 21 is configured using TFFs. The demultiplexing unit 21 includes a circulator 211, TFFs 214ai, and TFFs 214aj. The circulator 211 inputs the optical signal input from the second side to the TFF 214ai. The circulator 211 inputs the optical signal input from the TFF 214ai to the TFF 214aj. The circulator 211 inputs the optical signal input from the TFF 214aj to the detection unit 22. The configuration of the circulator 211 is as described above. The TFF 214ai transmits the optical signal of the first desired wavelength and reflects the optical signals of the second desired wavelength and the remaining wavelength. The TFF 214aj transmits the optical signal of the second desired wavelength and reflects the reflected remaining wavelength and the optical signal of the first desired wavelength that is not transmitted and reflected. Through such reflection and transmission, the desired demultiplexed signal and the remaining demultiplexed signal are separated from the demultiplexed input signal. Although FIG. 37 shows a configuration with two desired wavelengths, it may also be a configuration with three or more wavelengths.

[0174] Fig. 38 is a diagram showing an example of the configuration of an oblique incidence TFF 214. As shown in Fig. 38, wavelength components that travel straight on the same optical axis are separated from reflected wavelength components. For example, the desired separated signal of the first desired signal passes through the upper right lens as a straight wavelength component, while the second desired signal and the residual signal are reflected as reflected wavelength components and then pass through the lower left lens, and the desired separated signal of the second desired signal passes through. The reflected residual separated signal is output to the detector 22 via the lower right lens.

[0175] Therefore, the separation unit 21 may be configured without using a circulator by focusing each signal into a separate fiber. In particular, FIG. 38 illustrates a configuration in which a desired demultiplexed signal of a first desired signal, a desired demultiplexed signal of a second desired signal, and a residual demultiplexed signal are each focused from an input signal without using a circulator and output via separate fibers. Light from a user device may be incident on a TFF at a predetermined angle, and the reflected light, which is emitted at an angle that reflects the desired wavelength, may be focused on the output to the first side, while the reflected light, which is emitted at an angle that reflects the residual wavelength, may be input to the detection unit 22. This configuration may allow the separation unit 21 to be configured without using a circulator. For example, when the configuration shown in FIG. 36 is configured using a TFF 214 with oblique incidence, a signal of a suitable wavelength (desired demultiplexed signal) may be output from λj (lower left) in FIG. 38 by reflecting the suitable wavelength with a first filter and transmitting it with a second filter. In this case, λi (upper right) may be connected to the detection unit 22. In this case, the residual separated signal is output from λi (upper right). With this configuration, it is possible to realize a configuration equivalent to that shown in FIG. 36 without using a circulator. In this way, by using the oblique incidence TFF 214, the output destination of the collected light can be set to the detection unit 22 or the first side. Depending on the setting, it may be appropriately selected whether to reflect or transmit the appropriate wavelength (desired separated signal).

[0176] The oblique incidence TFF 214 shown in FIG. 38 may be used to configure the TFFs shown in FIGS. 35 to 37 and 39 that transmit a desired wavelength, or the TFFs shown in FIGS. 40 to 44 that reflect a desired wavelength, which will be described later.

[0177] Fig. 39 is a diagram showing a fourth configuration example in which the separator 21 is configured using TFFs. In the example shown in Fig. 39, the separator 21 includes a plurality of circulators 211 (for example, circulator 211a, circulator 211bi, and circulator 211bj) and a plurality of TFFs 214 (for example, TFFs 214ai, TFFs 214aj, TFFs 214bi, and TFFs 214bj). The circulator 211a inputs the optical signal input from the second side to the TFFs 214ai. The circulator 211a inputs the optical signal input from the TFFs 214ai to the TFFs 214aj. The circulator 211a inputs the optical signal input from the TFFs 214aj to the detection unit 22. Note that while Fig. 39 shows a two-stage cascade configuration for two wavelengths, a three or more stage cascade configuration for two wavelengths or a three or more stage cascade configuration may also be used.

[0178] The TFF 214ai passes the desired demultiplexed signal of the first desired signal among the optical signals input from the circulator 211a and inputs it to the circulator 211bi, and reflects the desired demultiplexed signal of the second desired signal and the residual demultiplexed signal, and inputs them to the circulator 211a. The circulator 211bi inputs the optical signals input from the TFF 214ai to the TFF 214bi. The circulator 211bi inputs the optical signals input from the TFF 214bi to the detection unit 22. The TFF 214bi outputs the desired demultiplexed signal of the first desired signal among the optical signals input from the circulator 211bi to the transmission path, and reflects the desired demultiplexed signal of the second desired signal and the residual demultiplexed signal, and output them to the detection unit 22.

[0179] The TFF 214aj passes the desired demultiplexed signal of the second desired signal out of the optical signals input from the circulator 211a and inputs it to the circulator 211bj, and reflects the residual demultiplexed signal and the remaining first desired signal, and inputs them to the circulator 211a. The circulator 211bj inputs the optical signals input from the TFF 214aj to the TFF 214bj. The circulator 211bj inputs the optical signals input from the TFF 214bj to the detection unit 22. The TFF 214bj outputs the desired demultiplexed signal of the second desired signal out of the optical signals input from the circulator 211bj to the transmission path and reflects the residual demultiplexed signal and the remaining first desired signal, and inputs them to the circulator 211bj. The output of the circulator 211bj is input to the detection unit 22.

[0180] With this configuration, the TFF 214bi can further remove optical signals of the second desired wavelength and residual wavelengths that were not completely removed by the TFF 214ai. Furthermore, the TFF 214bj can further remove optical signals of residual wavelengths that were not completely removed by the TFF 214aj. The detector 22 may receive only one output from the circulator 211a, the circulator 211bi, and the circulator 211bj, or any two or all of the outputs. For example, the outputs (desired separated signals) of the TFF 214bi and the TFF 214bj are suitable for estimating leakage of residual light (residual signals) into the desired separated signals. That is, the residual separated signals may be detected by reflection from either the upstream circulator 211a or the downstream circulators 211bi and 211bj. The intensity of the residual separated signals is greater in the upstream reflection than in the downstream reflection, resulting in higher sensitivity. In the case of reflection at the latter stage, the signal is not split again at the latter stage as in the case of the former stage, so it is easy to estimate leakage of the residual signal to the first side.

[0181] An isolator 23 may be provided between the separator 21 and the detector 22. The isolator 23 may be provided not only between the separator 21 and the detector 22, but also in a portion where reflection of an optical signal is not intended. For example, the isolator 23 may be provided between the TFF 214ai and the circulator 211bi, or the isolator 23 may be provided between the TFF 214bj and the circulator 211bj. Providing the isolator 23 in this manner is similar in other embodiments and other specific examples.

[0182] It should be noted that the circulators 211bi and 211bj do not necessarily have to be provided. In that case, the residual separated signals separated in the TFFs 214bi and 214bj are not input to the detector 22, so the accuracy of the processing in the detector 22 may be somewhat reduced, but it is possible to remove the remaining components of the residual signals from the desired separated signals. It should be noted that if the circulators 211bi and circulator 211bj are not provided, it is desirable to provide an isolator. It is particularly desirable to provide this isolator between the TFFs 214 and 214b.

[0183] The configurations of Figures 40, 41, 42 and 43, which use multilayer filters to reflect suitable wavelengths, are similar to the configurations of Figures 27, 28, 31 and 32, which use FBGs to reflect suitable wavelengths. Each will be explained below.

[0184] FIG. 40 is a diagram showing a fifth configuration example in which the demultiplexing unit 21 is configured using a TFF. The demultiplexing unit 21 includes a circulator 211 and a TFF 214. The circulator 211 inputs an optical signal input from the second side to the TFF 214. The circulator 211 outputs an optical signal input from the TFF 214 to the first side. The circulator 211 may be configured using, for example, an optical multiplexer / demultiplexer, as described in FIG. 27. Note that in the configuration using the TFF 214 and circulator 211 described below, the circulator 211 may also be configured as described above. The TFF 214 reflects an optical signal of a desired wavelength and transmits optical signals of a remaining wavelength. Through such reflection and transmission, the desired demultiplexed signal and the remaining demultiplexed signal are separated from the demultiplexed input signal.

[0185] FIG. 41 is a diagram illustrating a sixth configuration example in which the demultiplexing unit 21 is configured using TFFs. In the example illustrated in FIG. 41, the demultiplexing unit 21 includes a circulator 211 and a plurality of TFFs 214 (for example, two TFFs (TFF 214a and TFF 214b)). The circulator 211 inputs the optical signal input from the second side to the TFF 214a. The circulator 211 inputs the optical signal input from the TFF 214a to the TFF 214b. The circulator 211 outputs the optical signal input from the TFF 214b to the first side. The TFFs 214a and 214b reflect the optical signal of the desired wavelength and transmit the optical signals of the remaining wavelengths. By such reflection and transmission, the desired demultiplexed signal and the remaining demultiplexed signal are demultiplexed from the demultiplexed input signal. Note that although FIG. 41 illustrates a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0186] With this configuration, it is possible for the TFF 214b to further remove optical signals of residual wavelengths that could not be completely removed by the TFF 214a. The detection unit 22 may receive the output of either the TFF 214a or the TFF 214b, or both. When the detection unit 22 receives the output of only one of the TFFs 214a or 214b, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0187] 42 is a diagram showing a seventh configuration example in which the demultiplexing unit 21 is configured using TFFs. The demultiplexing unit 21 includes a circulator 211 and TFFs 214i and 214j. The circulator 211 inputs optical signals input from the second side to the TFFs 214i and 214j. The circulator 211 outputs optical signals input from the TFFs 214i and 214j to the first side, respectively. The TFF 214i reflects an optical signal of a first desired wavelength (first desired signal) and transmits optical signals of other wavelengths (second desired wavelength and remaining wavelengths). The TFF 214j reflects an optical signal of a second desired wavelength (second desired signal) and transmits optical signals of other wavelengths (the remaining wavelengths and the first desired wavelength that was not reflected by the preceding TFF 214i and transmitted).

[0188] FIG. 43 is a diagram showing an eighth configuration example in which the demultiplexer 21 is configured using TFFs. In the example shown in FIG. 43, the demultiplexer 21 includes a circulator 211 and a plurality of TFFs 214 (TFFs 214ai, 214aj, 214bi, and 214bj). The circulator 211 inputs an optical signal input from the second side to the TFF 214ai. The circulator 211 inputs an optical signal input from the TFF 214ai to the TFF 214bi. The circulator 211 outputs an optical signal input from the TFF 214bi to the first side. Although FIG. 30 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used. Note that a plurality of stages is desirable from the viewpoint of aligning the propagation delay.

[0189] The TFFs 214ai and 214bi reflect an optical signal of a first desired wavelength (first desired signal) among the optical signals input from the circulator 211 side, and transmit optical signals of other wavelengths (second desired wavelength and remaining wavelengths). The TFFs 214aj and 214bj reflect an optical signal of a second desired wavelength (second desired signal) among the optical signals input from the TFFs 214ai and 214bi, respectively, and transmit optical signals of other wavelengths (the remaining wavelengths and the first desired wavelength that was transmitted without being reflected by the preceding TFF 214ai or TFF 214bi). The TFFs 214ai and TFF 214bi input the light input from the TFFs 214aj and TFF 214bj, respectively, to the circulator 211. The transmitted light from the TFFs 214aj and TFF 214bj is output to the detection unit 22.

[0190] With this configuration, it is possible for the TFFs 214bi and 214bj to further remove optical signals of residual wavelengths that could not be completely removed by the TFFs 214ai and 214aj. The detection unit 22 may receive the output of either the TFFs 214aj or 214bj, or both. When the detection unit 22 receives the output of only one of the TFFs 214aj or 214bj, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0191] 32 and 34, the propagation delays of optical signals of multiple suitable wavelengths reflected by the TFF 214 may also be aligned to the same value in the configuration of FIG. 43. For example, the propagation delays of both wavelengths can be aligned by making the reflected wavelengths of the TFFs 214ai and 214bj the same, making the reflected wavelengths of the TFFs 214ai and 214bj the same, and making the sum of the propagation delays of the TFFs 214ai and 214bj equal to the sum of the propagation delays of the TFFs 214aj and 214bi. To align the sums of the propagation delays, for example, the propagation delays of the TFFs 214ai and 214bi, and the TFFs 214aj and 214bj may be configured to be the same.

[0192] [Example 3: AWG] First, we will explain AWG (Arrayed Waveguide Gratings).

[0193] An AWG is a transmission grating consisting of multiple waveguides of different lengths. Input waveguide(s), output waveguide(s), and fan-shaped slab waveguides are monolithically integrated on a substrate. Typically, such an AWG is fabricated using waveguides (e.g., quartz waveguides) on a silicon substrate. For example, an AWG may consist of input waveguide(s), slab waveguide, arrayed waveguide, and output waveguide(s). Light from the input waveguide(s) is diffracted by the input slab and propagates through the arrayed waveguides. The arrayed waveguides of the AWG are radially connected to the output slab. Light emitted from the AWG is focused at a position according to the input waveguide and wavelength.

[0194] The lengths of the multiple waveguides in the AWG are designed to increase by a constant amount, for example, ΔL. The phase difference between the waveguides depends on the wavelength. Since the focusing position varies depending on the wavelength, spectroscopic operation is obtained. For example, let d be the spacing between the AWG waveguides at the connection with the slab, f be the radius of curvature of the slab (i.e., the focal length), θ be the diffraction angle of the focused beam in the output slab, Δx be the spacing between the output waveguides, and nc and ns be the effective refractive indices of the channel waveguide and slab waveguide.

[0195] Under the condition that light from multiple waveguides arrives at the focal point in phase, the diffraction angle θ and wavelength satisfy the basic principle equation nc ΔL + ns d sinθ = m λ, where m is the diffraction order (an integer). In this equation, since θ is near zero, the diffraction order m is proportional to ΔL and is generally a large value of 10 or more. In order to increase the linear dispersion of a general diffraction grating, the pitch must be finer. Compared to such a general diffraction grating, with an AWG, it is possible to increase m by designing the length of the waveguide. Therefore, high resolution can be easily achieved with an AWG.

[0196] The free spectral range (FSR) is expressed as follows: FSR=c / (ng ΔL) Here, ng is the refractive index of the waveguide group, and is expressed as follows: Group refractive index of the waveguide ng: ng = nc - λ(dn / dλ)

[0197] where c is the speed of light in a vacuum. There are many transmission wavelengths with a period of FSR. Therefore, it is necessary to design the FSR to be wider than the number of multiplexed wavelengths x the multiplexing interval, and there is an upper limit to ΔL. When using a silica waveguide with a relative refractive index difference of around 1%, it is possible to create a DWDM wavelength multiplexer / demultiplexer with 80 wavelengths at 50 GHz intervals on a chip several centimeters square.

[0198] FIG. 44 is a diagram showing a first configuration example in which the separation unit 21 is configured using an AWG. The separation unit 21 includes an AWG 215. The AWG 215 outputs an optical signal input from the second side from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215, the output port from which the desired separated signal is output is connected to the first side. It is desirable that all remaining output ports are connected to the detection unit 22. This is to prevent the remaining separated signals from being overlooked in detection. An isolator 23 may be provided between the separation unit 21 and the detection unit 22. The isolator 23 may be provided, for example, between the AWG 215 and the optical multiplexer / demultiplexer. In this case, although the cost increases due to the increased number of isolators 23, a greater effect can be obtained.

[0199] In the figure, a single-input AWG is used, but a double-input AWG can also be used. In that case, to reduce the effects of reflection, unused ports should be terminated with a non-reflective termination or an isolator should be connected. This also applies to the following configurations.

[0200] FIG. 45 is a diagram showing a second configuration example in which the demultiplexing unit 21 is configured using an AWG. The demultiplexing unit 21 includes an AWG 215 and a multiplexing unit 216. The AWG 215 outputs an optical signal input from the second side from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215, the output port from which the desired demultiplexed signal is output is connected to the first side. The remaining output ports are connected to the multiplexing unit 216. The multiplexing unit 216 multiplexes the multiple residual demultiplexed signals input from the AWG 215 and outputs the multiplexed signal to the detecting unit 22. The multiplexing unit 216 may be any device configured to multiplex optical signals of multiple wavelengths. For example, the multiplexing unit 216 may be configured using an AWG. In this case, the multiple output ports from which the AWG 215 outputs the residual demultiplexed signals are connected to input ports of the multiplexing unit 216 (AWG) corresponding to the wavelengths of the respective residual signals. The multiplexing unit 216 may be configured using an optical multiplexer / branch. An isolator 23 may be provided between the separator 21 and the detector 22. Note that the multiplexer 216 should preferably have wavelength transmission characteristics equivalent to or less than those of the AWG 215, for example, one with greater crosstalk between adjacent channels, i.e., adjacent ports, in order to prevent output non-compatible wavelength components from being blocked by the multiplexer / demultiplexer and going undetected.

[0201] FIG. 46 is a diagram showing a third configuration example in which the separator 21 is configured using an AWG. The separator 21 includes a circulator 211, an AWG 215, and a reflector 217. The circulator 211 inputs the optical signal input from the second side to the AWG 215. The configuration of the circulator 211 is as described above. Of the multiple output ports of the AWG 215, the output port from which the desired demultiplexed signal is output is connected to the reflector 217. The remaining output ports are connected to the detector 22. The reflector 217 reflects the optical signal input from the AWG 215 (at least the desired demultiplexed signal). The reflected desired demultiplexed signal is input to the circulator 211 via the AWG 215. The reflector 217 may be configured using, for example, a total reflector, or a reflector that reflects a specific wavelength, such as an FBG, in this case at least a matching wavelength component. The reflector 217 may have any configuration as long as it is capable of reflecting the desired demultiplexed signal. The circulator 211 outputs the optical signal input from the AWG 215 to the first side.

[0202] In this configuration in which the desired signal is reflected by the reflecting section 217, the desired signal passes through the AWG 215 twice, so the ability to block wavelengths other than the desired one is roughly doubled compared to the original AWG 215. The insertion loss of the desired signal is doubled, and the reflectivity of the reflecting end is also reduced. If the reflection is imperfect, the reduction is proportional to that amount. For example, a 1% reduction occurs with 99% reflection, and a 0.1% reduction occurs with 99.9% reflection. The reflecting section may be a reflecting section that performs total reflection, or a reflecting section that reflects the desired wavelength (for example, an FBG or TFF that reflects the desired wavelength). Using a reflecting section that reflects the desired wavelength can improve the blocking ability. This also applies to the following embodiments.

[0203] 44, the outputs of the AWG 215 that are not output to the first side are input to the detection unit 22, but as in Fig. 45, some or all of the outputs may be aggregated via the multiplexer 216 and then input to the detection unit 22. This also applies to the following embodiments.

[0204] FIG. 47 is a diagram showing a fifth configuration example in which the demultiplexing unit 21 is configured using AWGs. The demultiplexing unit 21 includes a plurality of AWGs 215 and a plurality of multiplexing units 216. The AWG 215a outputs an optical signal input from the second side to the demultiplexing unit 21 from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215a, the output port from which an optical signal of a desired wavelength is output is connected to the input port of the next-stage AWG 215b (located relatively closer to the first side than the device itself). The remaining output ports of the AWG 215a are connected to the multiplexing unit 216a. The multiplexing unit 216a multiplexes the plurality of residual demultiplexed signals input from the AWG 215a and outputs the multiplexed signals to the detecting unit 22. Note that although FIG. 47 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0205] The AWG 215b outputs the optical signal (desired demultiplexed signal) input from the AWG 215a located at the previous stage (located relatively on the second side from the device itself) from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215b, the output port from which the optical signal of the desired wavelength is output is connected to the first side. The remaining output ports of the AWG 215b are connected to the multiplexing unit 216b. The multiplexing unit 216b multiplexes the multiple remaining demultiplexed signals input from the AWG 215b and outputs the multiplexed signals to the detecting unit 22.

[0206] With this configuration, it is possible for the AWG 215b to further remove optical signals of residual wavelengths that could not be completely removed by the AWG 215a. The detection unit 22 may receive the output of either the multiplexing unit 216a or the multiplexing unit 216b, or both. When the detection unit 22 receives the output of only one of the multiplexing units 216a and 216b, the other output may be configured as a non-reflection termination or may be connected to an isolator so as not to be reflected to the second side. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0207] Here, the outputs of AWG 215a and AWG 215b are aggregated via multiplexing unit 216 as in Fig. 45 before being input to detecting unit 22, but as in Fig. 44, the outputs of AWG 215 (AWG 215a) that do not output to the first side may be input to detecting unit 22 individually without going through multiplexing unit 216. Note that although the description is based on the configuration shown in Fig. 45, either one or both may be replaced with the configuration shown in Fig. 46. An example in which the front stage is replaced with the configuration shown in Fig. 46 and an example in which both are replaced with the configuration shown in Fig. 46 are shown in Figs. 48 and 49, respectively.

[0208] FIG. 48 is a diagram illustrating a sixth exemplary configuration in which the separator 21 is configured using an AWG. The configuration of FIG. 48 uses different AWGs 215, which has the advantage of allowing AWGs 215 with different transmission characteristics to be combined. For example, to make it easier to detect residual signal contamination, an AWG with a gentle wavelength transmission characteristic and overlapping transmission characteristics between adjacent channels may be used in the front stage (AWG 215a), and an AWG with better isolation between adjacent channels may be used in the rear stage (AWG 215b) so that residual signal contamination is reduced on the first side. Such a configuration is not limited to the configuration of FIG. 48, and is similar to the configurations shown in FIG. 47 and FIG. 49, for example.

[0209] The separating unit 21 includes a circulator 211, a plurality of AWGs 215, a multiplexing unit 216, and a reflecting unit 217. The circulator 211 inputs the optical signal input from the second side to the AWG 215a. The configuration of the circulator 211 is as described above. The AWG 215a outputs the optical signal input from the circulator 211 from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215a, the output port from which the optical signal of the desired wavelength is output is connected to the reflecting unit 217. The remaining output ports of the AWG 215a are connected to the detecting unit 22.

[0210] The reflector 217 reflects the optical signal (at least the desired demultiplexed signal) input from the AWG 215a. The reflected desired demultiplexed signal is input to the circulator 211 via the AWG 215a. The configuration of the reflector 217 is as described above. The circulator 211 outputs the optical signal (desired demultiplexed signal) input from the AWG 215a to the AWG 215b. The AWG 215b outputs the optical signal (desired demultiplexed signal) input from the circulator 211 from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215b, the output port from which the optical signal of the desired wavelength is output is connected to the first side. The remaining output ports of the AWG 215b are connected to the multiplexer 216. The multiplexer 216 multiplexes the multiple remaining demultiplexed signals input from the AWG 215b and outputs the multiple remaining demultiplexed signals to the detector 22.

[0211] With this configuration, the AWG 215b can further remove optical signals of residual wavelengths that could not be removed by the AWG 215a.

[0212] The outputs of the front stage (AWG215a) are input to the detection unit 22 individually, as in Figure 44, and the outputs of the rear stage (AWG215b) are aggregated via the multiplexing unit 216 before being input to the detection unit 22, as in Figure 45, but the output methods may be swapped between the front and rear stages, or one of the output methods may be unified.

[0213] The detection unit 22 may receive the output of either the AWG 215a or the multiplexer 216b, or both. When the detection unit 22 receives the output of either the AWG 215a or the multiplexer 216b, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0214] Fig. 49 is a diagram showing a seventh configuration example in which the separator 21 is configured using an AWG. The separator 21 includes a plurality of circulators 211, a plurality of AWGs 215, and a plurality of reflectors 217. The circulator 211a inputs the optical signal input from the second side to the AWG 215a. The configurations of the circulators 211a and 211b are as described above. The AWG 215a outputs the optical signal input from the circulator 211a from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215a, the output port from which the optical signal of the desired wavelength is output is connected to the reflector 217a. The remaining output ports of the AWG 215a are connected to the detector 22. Although Fig. 49 shows a two-stage cascade configuration, a three- or more-stage cascade configuration may also be used.

[0215] The reflector 217a reflects the optical signal (at least the desired demultiplexed signal) input from the AWG 215a. The reflected desired demultiplexed signal is input to the circulator 211a via the AWG 215a. The configurations of the reflector 217a and the reflector 217b are as described above. The circulator 211a inputs the optical signal (desired demultiplexed signal) input from the AWG 215a to the circulator 211b. The circulator 211b inputs the optical signal input from the circulator 211a to the AWG 215b. The AWG 215b outputs the optical signal (desired demultiplexed signal) input from the circulator 211b from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215b, the output port from which the optical signal of the desired wavelength is output is connected to the reflector 217b. The remaining output ports of the AWG 215b are connected to the detector 22.

[0216] In both the front stage (AWG215a) and the rear stage (AWG215b), the outputs of the AWG215 are input to the detection unit 22 individually, as in Figure 44, but for either or both of the AWG215, the outputs may be aggregated via the multiplexing unit 216 and then input to the detection unit 22, as in Figure 45.

[0217] The reflector 217b reflects the optical signal (at least the desired demultiplexed signal) input from the AWG 215b. The reflected desired demultiplexed signal is input to the circulator 211b via the AWG 215b. The circulator 211b outputs the optical signal (desired demultiplexed signal) input from the AWG 215b to the first side. The remaining output port of the AWG 215b is connected to the detector 22.

[0218] With this configuration, it is possible for the AWG 215b to further remove optical signals of residual wavelengths that could not be completely removed by the AWG 215a. The detection unit 22 may receive the output of either the AWG 215a or the AWG 215b, or both. When the detection unit 22 receives the output of only one of the AWGs 215a or the AWG 215b, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0219] 50 to 55, which will be described below, use desired signals of multiple wavelengths. For simplicity, the following description assumes that a first desired signal having a first desired wavelength λi and a second desired signal having a second desired wavelength λj are separated from the remaining signals.

[0220] In addition, when multiple inputs are combined, including an input having wavelength components that are only compatible with the first desired wavelength and an input having wavelength components that are only compatible with the second desired wavelength, it is not possible to detect the mixing of wavelength components that are incompatible with the second desired wavelength into the input having wavelength components that are only compatible with the first desired wavelength, or the mixing of wavelength components that are incompatible with the first desired wavelength into the input having wavelength components that are only compatible with the second desired wavelength. Furthermore, it is not possible to eliminate the leakage of the second desired wavelength into the path of the first desired wavelength, or the leakage of the first desired wavelength into the path of the second desired wavelength. In other words, these embodiments are applicable when the leakage of residual wavelengths between the desired wavelengths can be ignored.

[0221] 50 is a diagram showing an eighth configuration example in which the separator 21 is configured using an AWG. The separator 21 includes an AWG 215. The AWG 215 outputs an optical signal input from the second side from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215, the output port from which an optical signal of a first desired wavelength is output and the output port from which an optical signal of a second desired wavelength is output are connected to the first side. The remaining output ports are connected to the detector 22. An isolator 23 may be provided between the separator 21 and the detector 22.

[0222] 51 is a diagram showing a ninth configuration example in which the demultiplexing unit 21 is configured using an AWG. The demultiplexing unit 21 includes an AWG 215 and a plurality of multiplexing units 216. The AWG 215 outputs an optical signal input from the second side from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215, the output port from which an optical signal of a first desired wavelength is output and the output port from which an optical signal of a second desired wavelength is output are connected to the multiplexing unit 216b. The multiplexing unit 216b multiplexes the input desired demultiplexed signals (desired demultiplexed signals of the first desired signal and desired demultiplexed signals of the second desired signal) and outputs the multiplexed signals to the first side. The remaining output ports of the AWG 215 (output ports from which residual demultiplexed signals are output) are connected to the multiplexing unit 216a. The multiplexing unit 216a multiplexes the multiple residual demultiplexed signals input from the AWG 215 and outputs the multiplexed signals to the detecting unit 22. The configuration of the multiplexing unit 216 is as described above. An isolator 23 may be provided between the separation unit 21 and the detection unit 22.

[0223] The outputs of the AWG 215 may be input to the detector 22 individually, as in FIG. 50. The wavelength characteristics of the multiplexer 216a are the same as those connected to the detector 22 in the previous embodiment. The wavelength characteristics of the multiplexer 216b can be used in the same way as the AWG (AWG 215b) in the subsequent stage of FIG. 47, so from the perspective of improving blocking performance, it is preferable that the wavelength characteristics be the same as those of the AWG 215. However, the wavelength characteristics of the AWG 215 may be the same as the gradual previous stage (AWG 215a) in FIG. 47, and the wavelength characteristics of the multiplexer 216b may be the same as the less gradual subsequent stage (AWG 215b) in FIG. 47. Furthermore, the multiplexer 216b may be multiplexed using an optical multiplexer / demultiplexer, especially when the number of wavelengths of the desired wavelength is small and loss due to multiplexing is acceptable.

[0224] 52 is a diagram showing a tenth configuration example in which the separator 21 is configured using an AWG. The separator 21 includes a circulator 211, an AWG 215, and a plurality of reflectors 217. The number of reflectors 217 corresponds to the number of desired wavelengths to be used. The circulator 211 inputs the optical signal input from the second side to the AWG 215. The configuration of the circulator 211 is as described above. Of the plurality of output ports of the AWG 215, the output port from which the desired demultiplexed signal is output is connected to the reflector 217. Specifically, the output port from which the desired demultiplexed signal of the first desired signal is output is connected to the reflector 217a, and the output port from which the desired demultiplexed signal of the second desired signal is output is connected to the reflector 217b. The remaining output ports are connected to the detector 22.

[0225] Reflector 217a reflects the optical signal (at least the desired demultiplexed signal of the first desired signal) input from AWG 215. Reflector 217b reflects the optical signal (at least the desired demultiplexed signal of the second desired signal) input from AWG 215. The reflected desired demultiplexed signal of the first desired signal and the desired demultiplexed signal of the second desired signal are input to circulator 211 via AWG 215. The configurations of reflector 217a and reflector 217b are as described above. Circulator 211 outputs the optical signal (the desired demultiplexed signal of the first desired signal and the desired demultiplexed signal of the second desired signal) input from AWG 215 to the first side. In this configuration in which the desired demultiplexed signal is reflected by reflector 217, the ability to block wavelengths other than the desired one is roughly doubled. The insertion loss of the desired signal is doubled, and the reflectance of the reflecting end is also reduced. 51 may be provided between the AWG 215 and the detection unit 22. With this configuration, the multiplexing unit 216a can multiplex a plurality of residual separated signals of the AWG 215 into one residual separated signal and output the signal to the detection unit 23.

[0226] The configuration examples shown in Figures 50 to 52 may be connected in cascade. By configuring in this way, it is possible to improve the blocking ability. Specific examples of such configurations are shown in Figures 53 to 55.

[0227] 53 is a diagram showing a twelfth configuration example in which the demultiplexer 21 is configured using AWGs. The demultiplexer 21 includes a plurality of AWGs 215 and a plurality of multiplexers 216. The AWG 215a outputs optical signals input to the demultiplexer 21 from the second side from ports corresponding to the wavelengths. Of the plurality of output ports of the AWG 215a, the output port from which an optical signal of a desired wavelength is output is connected to the multiplexer 216b. Specifically, the output port from which a desired demultiplexed signal of the first desired signal is output and the output port from which a desired demultiplexed signal of the second desired signal is output are connected to the multiplexer 216b. The multiplexer 216b is connected to the input port of the AWG 215b. The multiplexer 216b multiplexes the input desired demultiplexed signal of the first desired signal and the input desired demultiplexed signal of the second desired signal, and outputs the multiplexed signal to the AWG 215b. The remaining output ports of the AWG 215a are connected to the multiplexer 216a. The multiplexer 216a multiplexes the plurality of residual separated signals input from the AWG 215a and outputs the multiplexed signal to the detector 22. Although Fig. 53 shows a two-stage cascade configuration, a three-stage or more cascade configuration may also be used.

[0228] The AWG 215b outputs the optical signal input from the multiplexer 216b (a multiplexed signal of the desired demultiplexed signal of the first desired signal and the desired demultiplexed signal of the second desired signal) from a port corresponding to the wavelength. Of the multiple output ports of the AWG 215b, the output port from which the optical signal of the desired wavelength is output is connected to the multiplexer 216d. Specifically, the output port from which the desired demultiplexed signal of the first desired signal is output and the output port from which the desired demultiplexed signal of the second desired signal is output are connected to the multiplexer 216d. The multiplexer 216d is connected to the first side. The multiplexer 216d multiplexes the input desired demultiplexed signal of the first desired signal and the desired demultiplexed signal of the second desired signal, and outputs the multiplexed signal to the first side. The remaining output ports of the AWG 215b are connected to the multiplexer 216c. The multiplexer 216c multiplexes the multiple residual demultiplexed signals input from the AWG 215b, and outputs the multiplexed signal to the detector 22.

[0229] Note that either or both of multiplexing unit 216a and multiplexing unit 216c may not necessarily be provided. In that case, the outputs of AWG 215 that are not provided with multiplexing unit 216 at a subsequent stage are not aggregated but are individually input to detection unit 22. Furthermore, multiplexing unit 216d may not necessarily be provided. In that case, the outputs to the first side of separation unit 215b are not aggregated but are individually output.

[0230] With this configuration, it is possible for the AWG 215b to further remove optical signals of residual wavelengths that could not be completely removed by the AWG 215a from the first desired signal and the second desired signal. The output of either the multiplexer 216a or the multiplexer 216b may be input to the detector 22, or both may be input. When the output of only one of the multiplexer 216a or the multiplexer 216b is input to the detector 22, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separator 21 and the detector 22.

[0231] 53 may be configured without the multiplexer 216. In this case, multiple (two in FIG. 53) desired demultiplexed signals output from the AWG 215a are input to different AWGs 215 (subsequent AWGs 215) instead of the AWG 215b. Such subsequent AWGs 215 may have configurations such as those shown in FIGS. 44 to 46. When the configuration of FIG. 45 is adopted, the multiplexer 216 is used together with the AWG 215, and when the configuration of FIG. 46 is adopted, the circulator 211 and the reflector 217 are used together with the AWG 215. Each AWG 215 has a configuration corresponding to the desired wavelength of each desired demultiplexed signal output from the AWG 215a. The output of the second wavelength side of the subsequent AWG 215 connected to the first wavelength side may be input to the detector 22, may be configured as a reflection-free termination, or may be discarded via an isolator. That is, the output on the second wavelength side of the subsequent AWG 215 connected to the first wavelength side may be configured not to be output to the first side. Also, the output on the first wavelength side of the subsequent AWG 215 connected to the second wavelength side may be input to the detecting unit 22, may be configured as a non-reflection termination, or may be discarded via an isolator. That is, the output on the first wavelength side of the subsequent AWG 215 connected to the second wavelength side may be configured not to be output to the first side.

[0232] 54 is a diagram showing a thirteenth configuration example in which the demultiplexing unit 21 is configured using an AWG. The demultiplexing unit 21 includes a circulator 211, a plurality of AWGs 215, a multiplexing unit 216, and a plurality of reflecting units 217. The circulator 211 inputs the optical signal input from the second side to the AWG 215a. The configuration of the circulator 211 is as described above. The AWG 215a outputs the optical signal input from the circulator 211 from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215a, the output port from which an optical signal of a desired wavelength is output is connected to the reflecting unit 217. Specifically, the output port from which a desired demultiplexed signal of the first desired signal is output is connected to the reflecting unit 217a, and the output port from which a desired demultiplexed signal of the second desired signal is output is connected to the reflecting unit 217b. The remaining output ports of the AWG 215a are connected to the detecting unit 22.

[0233] Reflector 217a reflects the optical signal (at least the desired demultiplexed signal of the first desired signal) input from AWG 215a. The reflected desired demultiplexed signal of the first desired signal is input to circulator 211 via AWG 215a. Reflector 217b reflects the optical signal (at least the desired demultiplexed signal of the second desired signal) input from AWG 215a. The reflected desired demultiplexed signal of the second desired signal is input to circulator 211 via AWG 215a. The configurations of reflector 217a and reflector 217b are as described above.

[0234] Circulator 211 outputs the optical signals (desired demultiplexed signals of the first desired signal and the second desired signal) input from AWG 215a to AWG 215b. AWG 215b outputs the optical signals (desired demultiplexed signals of the first desired signal and the second desired signal) input from circulator 211 from ports corresponding to the wavelengths. Of the multiple output ports of AWG 215b, the output port from which the optical signal of the first desired wavelength is output and the output port from which the optical signal of the second desired wavelength is output are connected to the first side. The remaining output ports of AWG 215b are connected to multiplexing unit 216. Multiplexing unit 216 multiplexes the multiple remaining demultiplexed signals input from AWG 215b and outputs the multiple remaining demultiplexed signals to detection unit 22.

[0235] With this configuration, the AWG 215b can further remove optical signals with residual wavelengths that could not be completely removed by the AWG 215a from the first and second desired signals. The detector 22 may receive either the output of the AWG 215a or the multiplexer 216, or both. When the detector 22 receives the output of either the AWG 215a or the multiplexer 216, the other output may be configured as a non-reflective termination or connected to an isolator. An isolator 23 may be provided between the separator 21 and the detector 22. A multiplexer 216 corresponding to the multiplexer 216b shown in FIG. 51 may be provided on the first side of the separator 215b. The multiplexer 216a shown in FIG. 51 may be connected to multiple output ports of the separator 215a for the residual demultiplexed signals. The multiplexer 216b shown in FIG. 51 may be connected to multiple output ports of the separator 215b for the desired demultiplexed signals.

[0236] 55 is a diagram showing a fourteenth configuration example in which the separator 21 is configured using an AWG. The separator 21 includes a plurality of circulators 211, a plurality of AWGs 215, and a plurality of reflectors 217. The circulator 211a inputs the optical signal input from the second side to the AWG 215a. The configurations of the circulators 211a and 211b are as described above. The AWG 215a outputs the optical signal input from the circulator 211a from a port corresponding to the wavelength. Of the plurality of output ports of the AWG 215a, the output port from which an optical signal of a desired wavelength is output is connected to the reflector 217. Specifically, the output port from which a desired demultiplexed signal of the first desired signal is output is connected to the reflector 217a, and the output port from which a desired demultiplexed signal of the second desired signal is output is connected to the reflector 217b. The remaining output ports of the AWG 215a are connected to the detector 22. Although FIG. 55 shows a two-stage cascade configuration, a three-stage or more cascade configuration may also be used.

[0237] Reflector 217a reflects the optical signal (at least the desired demultiplexed signal of the first desired signal) input from AWG 215a. The reflected desired demultiplexed signal of the first desired signal is input to circulator 211a via AWG 215a. Reflector 217b reflects the optical signal (at least the desired demultiplexed signal of the second desired signal) input from AWG 215b. The reflected desired demultiplexed signal of the second desired signal is input to circulator 211a via AWG 215a. The configurations of reflectors 217a to 217d are as described above.

[0238] Circulator 211a inputs the optical signals (desired demultiplexed signals of the first desired signal and the second desired signal) input from AWG 215a to circulator 211b. Circulator 211b inputs the optical signals input from circulator 211a to AWG 215b. AWG 215b outputs the optical signals (desired demultiplexed signals of the first desired signal and the second desired signal) input from circulator 211b from ports corresponding to the wavelengths. Of the multiple output ports of AWG 215b, the output port from which the optical signal of the desired wavelength is output is connected to reflector 217. Specifically, the output port from which the desired demultiplexed signal of the first desired signal is output is connected to reflector 217c, and the output port from which the desired demultiplexed signal of the second desired signal is output is connected to reflector 217d. The remaining output ports of AWG 215b are connected to detector 22.

[0239] Reflector 217c reflects the optical signal (at least the desired demultiplexed signal of the first desired signal) input from AWG 215b. The reflected desired demultiplexed signal of the first desired signal is input to circulator 211b via AWG 215b. Reflector 217d reflects the optical signal (at least the desired demultiplexed signal of the second desired signal) input from AWG 215b. The reflected desired demultiplexed signal of the second desired signal is input to circulator 211b via AWG 215b. Circulator 211b outputs the optical signals input from AWG 215b (the desired demultiplexed signal of the first desired signal and the desired demultiplexed signal of the second desired signal) to the first side. The remaining output port of AWG 215b is connected to detector 22.

[0240] With this configuration, it is possible for the AWG 215b to further remove optical signals of residual wavelengths that could not be completely removed by the AWG 215a from the first and second desired signals. The detector 22 may receive the output of either the AWG 215a or the AWG 215b, or both. When the detector 22 receives the output of only one of the AWGs 215a and 215b, the other output may be configured as a reflection-free termination or may be connected to an isolator. An isolator 23 may be provided between the separator 21 and the detector 22. A multiplexer 216 corresponding to the multiplexer 216a shown in FIG. 51 may be provided between the detectors of either or both of the AWGs 215a and 215b.

[0241] [Multiple port variant] Each of the above-described separators 21 has one input port. However, the separator 21 may have multiple input ports. An example configuration of the first embodiment having the separator 21 configured in this way will be described below.

[0242] [Multiple port modification of the first embodiment] FIG. 56 is a diagram illustrating a modification of the first embodiment of the demultiplexing system 11a. The demultiplexing unit 21 may be configured using a demultiplexing unit that outputs a different desired wavelength as a desired demultiplexed signal for each input port, such as a cyclic diffraction grating or a cyclic AWG. One of the multiple optical signals input to the optical distribution system 10a is input to each input port of the demultiplexing unit 21. Each optical signal is input to a selected input port where the desired wavelength is demultiplexed into a desired demultiplexed signal and the remaining wavelength is demultiplexed into a remaining demultiplexed signal. The demultiplexing unit 21 performs a demultiplexing process to wavelength-separate the input multiple optical signals into the desired signal and the remaining signal, thereby demultiplexing the optical signals input from the multiple ports into the desired demultiplexed signal and the remaining demultiplexed signal. The separated desired demultiplexed signal is input to the blocking device 30.

[0243] The detector 22 detects the optical intensity of the separated residual separated signals. When the detector 22 detects any of the residual separated signals with a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, indicating that the input optical signal (desired separated signal) should be blocked. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected with a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0244] When not blocking, the blocking device 30 passes each input optical signal (desired demultiplexed signal). Each desired demultiplexed signal that has passed through the blocking device 30 is output to the first side. When the blocking device 30 receives a control signal indicating blocking from the detection unit 22 of the demultiplexer 20, it blocks all input optical signals. In this case, none of the desired demultiplexed signals of the multiple optical signals input to the demultiplexing system 11a is output to the first side.

[0245] Here, in this modified example, if it is not possible to determine which input port the input from has been separated as the residual separation signal, the output can be stopped to some of the transmitting sides, or a separate cut-off device can be provided as shown in Figure 57 below and a portion can be cut off by the separate cut-off device, or output can be made to only some of the transmitting sides, or a separate cut-off device can be made conductive only to some of the transmitting sides, thereby identifying the port to which the signal separated as the residual separation signal has been input and preventing only that input from being output to the first side.

[0246] Fig. 57 is a diagram showing a modified example of the first embodiment of the separation system 11a. In the example of Fig. 57, an optical signal input to the separation system 11a is first input to one of a plurality of cutoff devices 30. One of the plurality of optical signals input to the separation system 11a is input to each cutoff device 30. A separation unit 21 having a plurality of input ports is connected to the subsequent stage (first side) of each cutoff device 30.

[0247] The demultiplexer 21 may be configured using, for example, an AWG. Of the multiple optical signals input to the demultiplexing system 11a, each input port of the demultiplexer 21 receives an optical signal that has passed through a cutoff device 30 connected to the upstream (second side) of the corresponding port. The demultiplexer 21 separates the multiple input optical signals into a desired demultiplexed signal and a residual demultiplexed signal by performing a demultiplexing process for wavelength-separating the desired signal from the residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0248] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the blocking device 30, indicating that the input optical signal (desired separated signal) should be blocked. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0249] When not blocking, the blocking device 30 passes each input optical signal. Each optical signal that passes through the blocking device 30 is output to the separation unit 21. When the blocking device 30 receives a control signal indicating blocking from the detection unit 22 of the separation device 20, it blocks the input optical signal. In this case, of the desired demultiplexed signals of the multiple optical signals input to the separation system 11a, the desired demultiplexed signals of the optical signals that are blocked by the blocking device 30 are not output to the first side. However, the desired demultiplexed signals of the optical signals that are not blocked are output to the first side. Note that in this configuration, all of the blocking devices 30 may be configured to block optical signals when the detection unit 22 detects any one of the remaining demultiplexed signals to have a predetermined optical intensity or higher.

[0250] In this manner, this configuration allows for control of the passage or blocking of multiple optical signals input to the separation system 11a for each individual cutoff device 30. For example, the detection unit 22 may detect a residual demultiplexed signal for an optical signal passing through each cutoff device 30 by turning on the cutoff devices 30 one by one in a predetermined order (by cutting off all of them and then unblocking them one by one). This configuration allows the detection unit 22 to identify which cutoff device 30 detected a residual demultiplexed signal with a predetermined intensity or greater from an optical signal passing through it. In this case, the detection unit 22 may determine to cut off the cutoff device 30 that was turned on at that time only when a residual demultiplexed signal is detected, or may notify the user device that is the source of the optical signal. Alternatively, the detection unit 22 may turn on all of the cutoff devices 30 and simultaneously detect the residual demultiplexed signals for all optical signals.

[0251] 58 is a diagram showing a modification of the first embodiment of the separation system 11a. In this example, a plurality of cutoff devices 30a are provided in the upstream (second side) of the separation device 20, and a cutoff device 30b is further provided in the downstream (first side) of the separation device 20.

[0252] An optical signal input to the separation system 11a is first input to one of a plurality of cutoff devices 30a. One of the plurality of optical signals input to the separation system 11a is input to each cutoff device 30a. A separation unit 21 having a plurality of input ports is connected to the subsequent stage (first side) of each cutoff device 30a.

[0253] The demultiplexer 21 may be configured using, for example, an AWG. Of the multiple optical signals input to the demultiplexing system 11a, each input port of the demultiplexer 21 receives an optical signal that has passed through a cutoff device 30a connected to the upstream (second side) of the demultiplexer 21's port. The demultiplexer 21 separates the multiple input optical signals into a desired demultiplexed signal and a residual demultiplexed signal by performing a demultiplexing process for wavelength-separating the desired signal from the residual signal. The separated desired demultiplexed signal is output to a cutoff device 30b provided at the downstream (first side) of the demultiplexer 20.

[0254] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it outputs a control signal to the cutoff device 30a or the cutoff device 30b, instructing the cutoff device 30a or 30b to cut off the input optical signal (desired separated signal). In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0255] When not blocking, the blocking devices 30a and 30b allow the input optical signals to pass. Each optical signal that passes through the blocking device 30a is output to the separation unit 21. When the blocking device 30a receives a control signal indicating blocking from the detection unit 22 of the separation device 20, it blocks the input optical signals. In this case, among the desired demultiplexing signals of the multiple optical signals input to the separation system 11a, the desired demultiplexing signals of the optical signals blocked by the blocking device 30a are not output to the first side. However, the desired demultiplexing signals of the optical signals that were not blocked are output to the first side. When the blocking device 30b receives a control signal indicating blocking from the detection unit 22 of the separation device 20, it blocks the input optical signals. In this case, none of the desired demultiplexing signals of the multiple optical signals input to the separation system 11a are output to the first side.

[0256] In this manner, with this configuration, it is possible to control the passage or blocking of multiple optical signals input to the separation system 11a for each individual cut-off device 30a. For example, the detection unit 22 may detect a residual demultiplexed signal for the optical signal passing through each cut-off device 30a by turning on the cut-off devices 30a one by one in a predetermined order (cutting off all of them and then unblocking them one by one). In this case, the detection unit 22 may determine to block the cut-off device 30a that was turned on at that time only when a residual demultiplexed signal is detected, or may notify the user device that is the source of the optical signal.

[0257] Alternatively, the detection unit 22 may turn on all the cutoff devices 30a and detect the residual demultiplexed signals of all optical signals collectively. In this case, the detection unit 22 may turn off the cutoff device 30b when a residual demultiplexed signal is detected, thereby collectively cutting off the optical signal (desired demultiplexed signal). Furthermore, even while the detection unit 22 is turning off the cutoff device 30b, the detection unit 22 may turn on all the cutoff devices 30a. This configuration makes it possible to continuously detect the state of each optical signal (demultiplexed input signal) (e.g., the intensity of the residual demultiplexed signal) while preventing the desired demultiplexed signal of the violating optical signal from flowing to the first side.

[0258] Next, a specific example of the configuration of the separator 21 having a plurality of input ports will be described. For example, the specific example described below may be applied to each separator 21 shown in Figures 56 to 58. In that case, the following description is for the purpose of explaining a specific example of the configuration of the separator 21, and therefore the cutoff device 30 is not shown, but the signals related to the separator 21 (such as the separated input signal and the desired separated signal) may be cut off by the cutoff device 30 shown in Figures 56 to 58.

[0259] 59 is a diagram showing a first configuration example in which the demultiplexing unit 21 in the modified example is configured using an AWG. The demultiplexing unit 21 includes an AWG 215 having a plurality of input ports. The AWG 215 outputs a plurality of optical signals input from an input port on the second side from output ports corresponding to the respective wavelengths. Of the plurality of output ports of the AWG 215, the output port from which an optical signal (desired signal) of a desired demultiplexed signal wavelength is output is connected to the first side. The remaining output ports are connected to the detection unit 22. For example, an AWG is used in which λ1, λ2, λ3, λ4, λ5 of input port 1 are output to output ports 1, 2, 3, 4, 5, λ1 of input port 2 are output to output ports 2, 3, 4, 5, 1, λ1 of input port 3 are output to output ports 3, 4, 5, 1, 2, λ1 of input port 4 are output to output ports 4, 5, 1, 2, 3, λ1 of input port 5 are output to output ports 5, 1, 2, 3, 4, and λ1 of input port 5 are output to output ports 5, 1, 2, 3, 4, and each user device (UT) is connected to the input port where the desired demultiplexed signal is output to the port connected to the cutoff device 30 and the residual demultiplexed signal is output to the detector 22, according to the set wavelength. That is, UTs with desired wavelengths of λ1, λ2, λ3, λ4, λ5 are connected to input ports 3, 4, 5, 1, 2, respectively. In this way, light of wavelengths corresponding to the remaining wavelengths of each UT is output to the detector. An isolator 23 may be provided between the separator 21 and the detector 22.

[0260] FIG. 60 is a diagram showing a second configuration example in which the demultiplexing unit 21 in the modified example is configured using an AWG. The demultiplexing unit 21 includes a circulator 211, an AWG 215 having multiple input ports, and a reflecting unit 217. The circulator 211 inputs an optical signal input from the second side to one input port of the AWG 215. The configuration of the circulator 211 is as described above. Of the multiple output ports of the AWG 215, the output port from which the desired demultiplexed signal is output is connected to the reflecting unit 217. The remaining output ports are connected to the detecting unit 22. The reflecting unit 217 reflects the optical signal input from the AWG 215 (at least the desired demultiplexed signal). The reflected desired demultiplexed signal is input to each circulator 211 via the AWG 215. The reflecting unit 217 may be configured using, for example, a total reflector or an FBG. Any configuration may be adopted for the reflecting unit 217 as long as it is capable of reflecting the desired demultiplexed signal. The circulator 211 outputs the optical signal input from the AWG 215 to the first side. Since this configuration has multiple inputs and multiple outputs, it is also possible to use a cascade configuration and connect the output of the first side of the previous stage to the input of the second side of the subsequent stage. Also, since this configuration has multiple inputs and multiple outputs, it is suitable for demultiplexing the desired demultiplexed signal in Figures 56 and 57. It is also possible to multiplex the first side with an optical multiplexer / demultiplexer or optical multiplexer / brancher, and use multiple inputs and a single output, which can be applied directly to Figures 56 and 57.

[0261] When configuring the demultiplexer 21 using an AWG as described above, the following considerations must be taken into account. From the perspective of detecting the presence of optical signals (residual signals) other than the desired wavelengths, the AWG must have a sufficiently wide range of residual wavelengths to be demultiplexed as residual signals. If the generation of light of wavelengths other than the input wavelength, such as four-wave mixing due to nonlinear optical effects or the Raman effect, is not taken into consideration, it is desirable that the AWG used cover all of the desired wavelengths and residual wavelengths. If such generation is taken into consideration, it is also desirable that the AWG cover all influencing wavelengths, including the generated light.

[0262] When a cyclic AWG is used, the cyclic period may be configured to be sufficiently wider than the residual wavelength to be detected so that the residual wavelength is not output from the output port of the desired wavelength. A filter may be provided to block the residual signal so that the residual wavelength is not output from the port of the desired wavelength and reaches the detection unit 22. For example, a wide AWG and a narrow AWG may be cascaded. For example, the wavelength that is transmitted may be the only wavelength available. For example, a BPF that transmits only wavelengths corresponding to some of the cyclic periods may be cascaded with an AWG.

[0263] However, if wavelengths circulating through the same port are set, it is possible to treat multiple wavelengths as desired wavelengths, as described below. However, if the wavelengths demultiplexed into the same port include the desired wavelength and residual wavelengths, BPFs or AWGs may be cascaded to transmit only the desired wavelength.

[0264] If the AWG is made of glass, it is possible to change the refractive index by changing the temperature, thereby changing the wavelength treated as the desired wavelength. If the AWG is made of semiconductor, it is possible to change the refractive index by changing the temperature or applying a voltage, thereby changing the wavelength treated as the desired wavelength. In addition, it is possible to change the wavelength treated as the desired wavelength by switching the connection between the input or output ports.

[0265] To detect leakage of wavelengths in the cutoff band between AWG ports, an AWG with a large crosstalk XT between adjacent ports (e.g., 3 dB) may be used. When multiple AWGs are cascaded, an AWG with a large crosstalk XT may be used for monitoring purposes as the front-stage AWG, and an AWG with a small crosstalk XT may be used as the rear-stage AWG. With this configuration, it is desirable to mainly detect the output of adjacent ports using the front-stage AWG.

[0266] Other diffraction gratings may be used instead of the AWG described above. For example, a reflective diffraction grating on a waveguide may be used, a spatially coupled transmission diffraction grating may be used, or a spatially coupled reflection diffraction grating may be used. For example, a spatial modulation element whose transmission angle varies depending on wavelength, such as a spatially coupled transmission diffraction grating or LCOS (Liquid Crystal on Silicon), may be used instead of the AWG. In this case, the output port is replaced by the angular range of the output light. Alternatively, a spatially coupled reflection diffraction grating that reflects the desired signal and the residual signal at different angles may be used instead of the AWG. Alternatively, a spatial modulation element whose reflection angle varies depending on wavelength may be used instead of the AWG. The reflected light at the angle of the desired signal may be collected, and the reflected light at the angle of the residual signal may be collected and output to the detector 22. The desired and residual separated signals are separated from the separated input signal through such reflection and transmission. Below, a typical spatially coupled reflection diffraction grating will be described.

[0267] The relationship between the wavelength λ diffracted by a diffraction grating with a grating spacing d and the diffraction angle θ is expressed by the following equation (1). mλ=d(sinθ-sinφ)...Equation (1)

[0268] Here, m is the diffraction order and φ is the angle of incidence on the diffraction grating. If the incident optical axis is fixed, the angle of incidence φ is constant when the diffraction grating is fixed. To find the relationship between the diffraction angle θ and the wavelength λ, equation (1) is differentiated to obtain the following equation (2). mΔλ=dcosθ·Δθ····Formula (2)

[0269] The width of the photodetector is x, and the distance to the photodetector (or the focal length of the focusing mirror) is L. If the photodetector can separate light within the range Δθ in equation (2), then the width x can be expressed by the following equation (3). x=ΔθL Equation (3)

[0270] Generally, m = 1. Therefore, from equations (2) and (3), the wavelength range Δλ that can be separated is expressed as follows: Δλ=xdcosθ / L Equation (4)

[0271] If the detector width x = 10 mm, d = 1 μm, cosθ = 0.5, and L = 300 mm, the wavelength range Δλ is 17 nm. If the detector has 256 elements, the wavelength resolution can be expressed as follows: 17 nm ÷ 256 ≒ 70 pm.

[0272] The diffraction grating may be either a surface relief diffraction grating, which has a concave-convex surface, or a planar diffraction grating, which has a flat surface and periodically changes the refractive index or transmittance within the element. It may also be either a transmission or reflection type. Transmission types are created by scratching or etching repeated parallel structures into a transparent substrate. Transmission types create regions where light scatters. The general equation for a diffraction grating at an incident angle of 0 degrees is α [sinθm - sinθi] = mλ (grating spacing α, diffraction order m, exit angle θm from the surface normal, and incident angle θi).

[0273] Reflection gratings are traditionally made by cutting parallel grooves into the surface of a metal-coated optical element. Reflection gratings can also be made by imprinting a master onto epoxy or plastic. The formula for a reflection grating is α [sinθm + sinθi]=mλ. Both reflection and transmission gratings have no wavelength dependence for the zeroth order of light, since there is no diffraction pattern. Therefore, both reflection and transmission gratings are used for other orders.

[0274] The spacing of the diffraction grating is d, its depth is h, the refractive index of the diffraction grating portion is n, the angle of incidence of light onto the diffraction grating is θi, the wavelength of the light is λ, and the thickness of the planar grating is t. When the direction of the electric vector of the incident light is within the plane of incidence, it is called p-polarization, and when the electric vector is perpendicular to the plane of incidence, it is called s-polarization. When light of wavelength λ is incident on a diffraction grating, the diffracted light constructively interacts with the light diffracted by adjacent grooves when the optical path difference is an integer multiple of λ. The following equation holds between the angle of incidence and the angle of diffraction: ni·(sinθm-sinθi)=mλ / d(mm=0,±1,±2,±3···). Here, θm is the diffraction angle of the m-th order diffracted light. The angle of the diffracted light is positive when it is on the opposite side of the grating normal to the incident light, and negative when it is on the same side as the incident light. Furthermore, the order m of the diffracted light is positive when the diffraction angle is larger than the zero-th order diffracted light, and negative when the diffraction angle is smaller. Normally, the incident light is in the air, so ni = 1.

[0275] Fig. 61 is a diagram showing a modified example of an AWG. In the modified example of the AWG shown in Fig. 61, multiple output waveguides are used as a single output. In this embodiment, the AWG may be configured as shown in Fig. 61. In the AWG shown in Fig. 61, the width of the receiving side of the output waveguide that separates the remaining wavelengths is increased to more than one wavelength, and outputs of multiple wavelengths that are not the desired wavelength can be output together.

[0276] This AWG outputs the desired wavelength band and other wavelength bands from different ports. By applying such an AWG to the separation unit 21, it is possible to reduce the number of detection units 22, the number of reflection-free termination points, the number of multiplexed AWGs, the number of reflection points, etc. In such an AWG, multiple outputs may be bundled, for example, by wavelength. Furthermore, the range of wavelengths to be aggregated is equal to or greater than the wavelength range in which mismatched wavelength components must be detected. For example, the desired wavelength may be sandwiched between residual wavelengths, and output port 2 of the AWG may be used to output the desired wavelength, while output ports 1 and 3, located on either side of output port 2, may be used to output the residual separated wavelengths. The outputs of output port 1 and output port 3 may be multiplexed. While the example shows one port on the short wavelength side and one port on the long wavelength side for outputting the residual wavelengths, the number of ports is not necessarily limited to one. Bundling (aggregating) multiple outputs by wavelength allows for a reduction in the number of ports, which is advantageous.

[0277] 62 and 63 are diagrams showing configuration examples of the demultiplexer 21 using the AWG configured as in FIG. 61. In FIGS. 62 and 63, an AWG configured as in FIG. 61 is applied to an AWG shown as AWG 215. The configuration shown in FIG. 62 is substantially similar to the configuration of the demultiplexer 21 described with reference to FIG. 44, in which the number of output ports of the AWG 215 to the detection unit 22 is set to two. The configuration shown in FIG. 63 is substantially similar to the configuration of the demultiplexer 21 described with reference to FIG. 46, in which the number of output ports of the AWG 215 to the detection unit 22 is set to two.

[0278] This point will be explained in detail. The configuration in FIG. 44 assumes an AWG that demultiplexes and outputs different wavelengths at FSR intervals. While five wavelengths are illustrated in FIG. 44, ports are provided for the wavelengths to be demultiplexed as desired wavelengths and the number of wavelengths to be detected as residual wavelengths is equal to the number of ports. If the wavelength band to be detected is 32 wavelengths, one port is required for the desired wavelength and 31 ports for the residual wavelengths. This poses a problem of requiring a large number of connection lines to the detection unit 22. To solve this problem, in the configuration in FIG. 45, ports corresponding to the residual wavelengths are multiplexed in the multiplexer 216 before being passed to the detection unit 22. In such a configuration, loss in the multiplexer 216 may degrade the detection sensitivity of the detection unit 22. For example, if the number of ports is 2^N (2 to the Nth power), a branching loss of 3N dB occurs. As mentioned above, if there are 32 ports, N = 5, and the loss is 15 dB (≈ 1 / 32). The multiplexing section uses a multiplexing section 216 whose characteristics generally match those of the AWG 215. However, there is a problem in that the multiplexing section 216 is still required in FIG.

[0279] Therefore, in the modified AWG shown in Fig. 61, the ports that output the remaining wavelengths on the longer wavelength side of the desired wavelength and the shorter wavelength side of the desired wavelength output wavelengths together for multiple FSRs. In the case of AWG 215 in Fig. 44, at least one of the two upper ports or the two lower ports of AWG 215 is combined into one port. Either the upper or lower port has a wavelength longer than the desired wavelength, and the opposite port has a shorter wavelength. If each can be combined into one port, the multiplexer 216 required in the configuration of Fig. 45 is not necessary, and the number of wires between the detector 22 is reduced to two, half the four wires required in Fig. 44.

[0280] 64 and 67 are diagrams showing specific examples of the separation unit 21 configured using a reflective diffraction grating. In the specific example of the diffraction grating shown in FIG. 64, the desired separated signal passes through the diffraction grating and is output to the first side from the right end of the figure. The residual separated signal passes through the diffraction grating and is input to the detection unit 22 from the right end of the figure. Such a diffraction grating may be applied, for example, in place of the AWG 215 shown in FIGS. 44, 45, 47, 50, 51, and 53, or may be applied in place of the AWG 215b in FIG. 48 or the AWG 215215b in FIG. 54. In the specific example of the diffraction grating shown in FIG. 65, the desired separated signal is reflected by the reflector 217 located at the right end of the diffraction grating shown in the figure, and is output from the left end of the diffraction grating to the first side via the circulator 211. The residual separated signal passes through the diffraction grating and is input to the detection unit 22 from the right end of the figure. Such a diffraction grating may be used in place of the AWG 215 shown in Figures 46, 49, 52, and 55, or may be used in place of the AWG 215a in Figure 48 or the AWG 215a in Figure 54. In these configurations, multiple outputs may be bundled and aggregated by wavelength. In this case, the range of wavelengths aggregated is equal to or greater than the wavelength range in which non-compliant light must be detected. Although Figures 63 and 64 illustrate single-input and multiple-output configurations, multiple-input and multiple-output configurations are also applicable to Figures 59 and 60, which use multiple-input and multiple-output AWGs.

[0281] [Example 4: Waveguide-type ring resonator] The separator 21 may be configured using a waveguide-type ring resonator. For example, a micro ring resonator (MRR) with a resonator length of several tens of micrometers and a resonant wavelength interval (free spectral range: FSR) of several tens of nanometers may be used. The shape of the ring resonator section may not be a perfect circle, but may be a racetrack shape with the coupling section as a parallel linear waveguide. This configuration makes it easier to design the coupling coefficient at the coupling section.

[0282] A waveguide-type ring resonator may be serially coupled. In serial coupling, multiple rings are provided. In the following description, the specific example of FIG. 66 describes an example of a waveguide-type ring resonator using one ring, and the specific example of FIG. 67 describes an example of a waveguide-type ring resonator using multiple rings. Note that multiple rings may be used in the example shown in FIG. 66 , and one ring may be used in the example shown in FIG. 67 . This configuration enables spectral characteristics with a flat passband, a steep transition (roll-off) from the passband to the stopband, and sufficient stoppage. However, the coupling coefficient between the bus line waveguide and the microring, and the coupling coefficient between one microring and another microring, must satisfy a certain condition known as the Butterworth condition. A double ring is a specific example of serial coupling that increases the Q value, which represents the degree of resonance, while widening the passband (the range of wavelengths selected).

[0283] FIG. 66 is a diagram showing a first configuration example in which the separator 21 is configured using a waveguide-type ring resonator. The separator 21 includes a waveguide-type ring resonator 218. The waveguide-type ring resonator 218 receives an optical signal from the second side through its upper left port and outputs a desired separated signal and a residual separated signal from different ports. Specifically, the waveguide-type ring resonator 218 outputs the desired separated signal to the first side from its lower left port (drop port) in FIG. 68 and outputs the residual separated signal to the detector 22 from its upper right port (thru port). It is desirable to connect a reflectionless termination or an isolator to the lower right port.

[0284] Fig. 67 is a diagram showing a second configuration example in which the separator 21 is configured using a waveguide-type ring resonator. In the example shown in Fig. 67, the separator 21 includes a circulator 211, a reflector 217, and a waveguide-type ring resonator 218. The circulator 211 inputs an optical signal input from the second side to the waveguide-type ring resonator 218. When an optical signal is input to the upper left input port of the waveguide-type ring resonator 218, the waveguide-type ring resonator 218 outputs a desired separated signal and a residual separated signal separated from the input optical signal from different ports. Specifically, the waveguide-type ring resonator 218 outputs the desired separated signal from the lower left port (drop port) in Fig. 67 to the reflector 217, and outputs the residual separated signal from the upper right port (thru port) to the detector 22.

[0285] When an optical signal (desired demultiplexed signal) is input from the waveguide-type ring resonator 218, the reflector 217 reflects the input optical signal and outputs it to the waveguide-type ring resonator 218. The waveguide-type ring resonator 218 receives the reflected optical signal (desired demultiplexed signal) from the lower left drop port and outputs it to the circulator 211 from the upper left port. The circulator 211 outputs the optical signal (desired demultiplexed signal) input from the waveguide-type ring resonator 218 to the first side.

[0286] [Example 5: Lattice-type optical filter] The demultiplexer 21 may be configured using a lattice optical filter. The lattice optical filter is configured, for example, with a delay line, a symmetric Mach-Zehnder interferometer type variable coupling ratio coupler, and a phase adjustment unit. By changing the phase shift value of the optical filter, any filter characteristic can be obtained with the performance upper limit determined by the asymmetric Mach-Zehnder interferometer. The property that the characteristics appear periodically for each FSR (Free Spectral Range) determined by ΔL is utilized. In a lattice type, the path length difference between each asymmetric MZI constituting the lattice is ΔL. In a transversal type, the length of the delay imparting unit between each branch is ΔL. In an AWG, the difference in length between one waveguide constituting the arrayed waveguide and an adjacent waveguide (for example, i and i-1, i and i+1 in the arrayed waveguide in Figure 61) is ΔL.

[0287] If the period is short, it can be realized by combining multiple filters, as in the case of a periodic AWG.To eliminate polarization dependency, it can be realized as a reflective type by installing a circulator and a Faraday rotating mirror with a rotation angle of 90 degrees at the input and output terminals.

[0288] 68 is a diagram showing a first configuration example in which the demultiplexer 21 is configured using a lattice optical filter. The demultiplexer 21 includes a lattice optical filter 219. The lattice optical filter 219 receives an optical signal from the second side and outputs a desired demultiplexed signal and a residual demultiplexed signal from different ports. Specifically, the lattice optical filter 219 outputs the desired demultiplexed signal to the first side from a first port and outputs the residual demultiplexed signal from a second port to the detector 22. The delay ΔL of the delay arm of the lattice filter, the coupling ratio of the variable coupling ratio coupler, and the phase θ of the phase shifter are adjusted so that the first port outputs a compatible wavelength component and the second port outputs an incompatible wavelength component. In addition, in the case of a lattice filter, the delay ΔL of the delay adding unit, the coupling ratio of the tap (variable coupling ratio coupler), and the phase of the phase shifter may be adjusted.

[0289] Fig. 69 is a diagram showing a second configuration example in which the demultiplexing unit 21 is configured using a lattice optical filter. In the example shown in Fig. 69, the demultiplexing unit 21 includes a circulator 211, a reflector 217, and a lattice optical filter 219. The circulator 211 inputs an optical signal input from the second side to the lattice optical filter 219. When an optical signal is input from the input port, the lattice optical filter 219 outputs a desired demultiplexed signal and a residual demultiplexed signal, which are demultiplexed from the input optical signal, from different ports. Specifically, the lattice optical filter 219 outputs the desired demultiplexed signal from the first port to the reflector 217, and outputs the residual demultiplexed signal from the second port to the detection unit 22.

[0290] When an optical signal (desired demultiplexed signal) is input from the lattice optical filter 219, the reflector 217 reflects the input optical signal (at least the appropriate wavelength component thereof) and outputs it to the lattice optical filter 219. The lattice optical filter 219 inputs the reflected optical signal (desired demultiplexed signal) and inputs it to the circulator 211. The circulator 211 outputs the optical signal (desired demultiplexed signal) input from the lattice optical filter 219 to the first side. In each of the configurations shown in FIGS. 66, 67, 68 and 69, it is desirable that the open ends in the figures be non-reflection terminated in order to suppress the effects of reflection.

[0291] [Variations] Fig. 70 is a diagram showing a specific example of the configuration when the demultiplexer 21 is configured using a demultiplexer with high polarization dependency. In this case, the demultiplexer 20 includes multiple demultiplexers 21 and multiple PBSs (Polarization Beam Splitters) 2110. An optical signal input to the demultiplexer 20 is input to the PBS 2110a. The PBS 2110a splits the optical signal into predetermined polarizations. In the example of Fig. 70, the optical signal is split into two.

[0292] The PBS 2110a inputs one polarized wave to the separator 21a and inputs the other polarized wave to the separator 21b. The separators 21a and 21b each separate a desired separated signal and a residual separated signal. The separators 21a and 21b output the residual separated signal to the PBS 2110b and the desired separated signal to the PBS 2110c. The PBS 2110b performs polarization combining on the residual separated signals input from each separator 21 and outputs the combined signals to the detector 22. The PBS 2110c performs polarization combining on the desired separated signals input from each separator 21 and outputs the combined signals to the first side. Note that the PBS 2110b may output the residual separated signals input from each separator 21 separately to the detector 22 without performing polarization combining or combining. Instead of adopting the configuration shown in FIG. 70, a half-wave plate that switches the polarization between the first half and the second half and compensates for the birefringence of the optical waveguide, like an AWG, may be provided midway along the path.

[0293] [Application example to PG] An example of the configuration when the first embodiment (light sorting system 10a) of the light sorting system 10 described above is applied to a PG will be described below.

[0294] In the optical distribution system 10a, the desired wavelength may be a wavelength set for the user device from the PG. In such a configuration, the desired wavelength may change before and after being set. In such a case, the wavelengths separated in the demultiplexing process (the wavelengths transmitted as conforming (desired wavelengths) and the wavelengths filtered and detected as non-conforming (residual wavelengths)) change. The optical distribution system 10a may be notified of the desired wavelength from a device controlling the wavelength of each user device through communication using a predetermined carrier, through AMCC, or via a specific communication route. This notification may be performed by electrically or optically multiplexing a control bit of a transmission frame using time division multiplexing or frequency division multiplexing such as AMCC on a signal exchanged between the user device and a functional unit controlling the user device or a corresponding device, or by polarization modulation, or by orthogonal polarization multiplexing or wavelength division multiplexing using light different from the signal, or by a path different from the signal, such as wireless or wired.

[0295] Here, we will explain the wavelength (wavelength treated as suitable: desired wavelength) that the demultiplexer 21 allows the user equipment to communicate with. If the connection between the user equipment and the PG control unit is via a monitoring unit downstream of the output of the optical demultiplexer 40, in the demultiplexer system 11 that is arranged at least on the path to the monitoring unit downstream of the output of the optical demultiplexer 40, this is the wavelength used for the initial connection at the time of initial connection, and once the wavelength has been set to the user equipment, this is the set (instructed) wavelength.

[0296] If the connection between the user equipment and the control unit of the PG is via the optical distribution device 40 (the basic configuration of the PG, changing the SW connection to switch between connecting to the control unit or connecting to the opposing device), then in the separation system 11 located at least on the path to the optical distribution device 40, at the time of initial connection, it is the wavelength used for the initial connection, and after the wavelength has been set to the user equipment, it is the set (instructed) wavelength.

[0297] If the connection between the user equipment and the control unit of the PG is via a monitoring unit before the input of the optical distribution device 40, in the separation system 11 that is placed at least on the path to the monitoring unit before the input of the optical distribution device 40, at the time of initial connection, it is the wavelength used for the initial connection, and after the wavelength has been set to the user equipment, it is the set (instructed) wavelength.

[0298] The demultiplexer 21 or the detector 22 may communicate with the control unit of the PG. The control unit of the PG controls the wavelength (desired wavelength) set in the user device. In this case, the demultiplexer 21 or the detector 22 communicates with the control unit using an optical signal of the wavelength used for the initial connection at the time of initial connection (when no wavelength is set in the user device), and after a wavelength is set in the user device, communicates with the control unit using an optical signal of that wavelength (desired wavelength). In this case, if the wavelength set for the user device by the PG is changed as described above, the wavelength of the optical signal used when the control unit of the PG and the demultiplexer 21 or the detector 22 communicate also changes accordingly.

[0299] However, the configuration is not limited to this, and the demultiplexer 21 or detector 22 may communicate with the control unit of the PG at a wavelength different from the desired wavelength set in the user device. In this configuration, even if the wavelength set from the PG to the user device is changed, the wavelength of the optical signal used when the control unit of the PG communicates with the demultiplexer 21 or detector 22 does not change.

[0300] Next, we will explain communication between the demultiplexer 21 and the control unit. If the control signal for the demultiplexer 21 is not superimposed on the signal light from the user equipment or is not multiplexed with light that is treated as having the same wavelength as the user equipment, communication is possible regardless of the wavelength setting for the user equipment, without going through any wavelength-dependent device including the demultiplexer 21 itself.

[0301] When the control signal to the demultiplexer 21 is superimposed on the signal light from the user equipment without passing through any wavelength-dependent device including the demultiplexer 21 itself, communication is possible at the wavelength set for the user equipment (when the demultiplexer 21 blocks wavelengths other than those set from the user equipment).

[0302] If the control signal to the demultiplexer 21 is not superimposed on the signal light from the user equipment via a wavelength-dependent device including the demultiplexer 21 itself, but is not multiplexed with light that is treated as having the same wavelength as the user equipment, communication is possible at a wavelength that is conductive to the control unit in the wavelength-dependent device (this is the case when the demultiplexer 21 blocks wavelengths other than those set from the user equipment).

[0303] When the control signal to the demultiplexer 21 is superimposed on the signal light from the user equipment via a wavelength-dependent device including the demultiplexer 21 itself or multiplexed with light that is treated as having the same wavelength as the user equipment, communication is possible at a wavelength that is conductive to the control unit in the wavelength-dependent device and that is in accordance with the wavelength setting for the user equipment (this is the case when the demultiplexer 21 blocks wavelengths other than those set from the user equipment).

[0304] For example, in the initial stage before setting, if the demultiplexer 21 does not block wavelengths other than those set from the user equipment and does not pass through wavelength-dependent devices including the demultiplexer 21 itself, communication is possible regardless of the wavelength setting for the user equipment.

[0305] For example, in the initial stage before setting, if the separation unit does not block wavelengths other than those set from the user equipment and passes through a wavelength-dependent device including the separation unit 21 itself, communication is possible at a wavelength that is conductive to the control unit through the wavelength-dependent device.

[0306] For example, if the demultiplexer 20 is located as shown below, in communication with the PG control unit, the wavelength used for the initial connection is used at the time of initial connection, and once the wavelength has been set in the user device, the set wavelength is used. If the connection is made via a function (e.g., a monitoring unit) located downstream of the optical sorting device 40, the position is at least as far as the monitoring unit located downstream of the optical sorting device 40. If the connection is made via inside the optical sorting device 40, the position is at least as far as the optical sorting device 40. If the connection is made via a monitoring unit located upstream of the input of the optical sorting device 40 (on the user device side), the position is at least as far as the optical sorting device 40.

[0307] If the connection between the user equipment and the control unit of the PG is made at a stage subsequent to the output of the optical distribution device 40, in the separation system 11 arranged at least on the path to the connection point after the output of the optical distribution device 40, at the time of initial connection, it is the wavelength used for the initial connection, and after the wavelength has been set to the user equipment, it is the set (instructed) wavelength.

[0308] If the connection between the user equipment and the control unit of the PG is made by switching at the optical distribution device 40, at least in the separation system 11 arranged on the path to the optical distribution device 40, at the time of initial connection, it is the wavelength used for the initial connection, and after the wavelength has been set to the user equipment, it is the set (instructed) wavelength.

[0309] If the connection between the user equipment and the control unit of the PG is made before the input to the optical distribution device 40, in the separation system 11 placed at least on the path to the connection point before the input to the optical distribution device 40, at the time of initial connection, it is the wavelength used for the initial connection, and after the wavelength has been set to the user equipment, it is the set (instructed) wavelength.

[0310] If the demultiplexer 20 is installed in the add-on package 41, the wavelength used for the initial connection is used at the time of initial connection, and once the wavelength has been set in the user device, the wavelength set in the user device is used. Even in this configuration, the desired wavelength may change before and after being set. In this case, the wavelengths separated in the demultiplexing process (the wavelengths transmitted as conforming (desired wavelengths) and the wavelengths filtered and detected as non-conforming (residual wavelengths)) will change.

[0311] In Figure 9, if the separation device 20 is installed on the second side of the cut-off device 30 and the propagation delay of light from the user device from the separation device 20 to the cut-off device 30 can be made greater than the sum of the processing time for detecting the intensity of the light separated as an incompatible wavelength component by the separation device 20 and determining whether to cut it off, the propagation time for the notification from the detector to the cut-off device 30, and the cut-off processing time of the cut-off device 30, it will be possible to prevent incompatible optical signals from flowing beyond the cut-off device 30.

[0312] To prevent such inflow, a delay device may be used, for example, as follows. After the residual separated signal is detected by the detector 22 of the demultiplexer 20, the optical signal or the desired separated signal may be delayed by a delay device so that the optical signal containing the residual signal or the desired separated signal separated from the optical signal can be blocked by the cutoff device 30. This configuration makes it possible to gain time from the detection of the residual separated signal to the cutoff control, and to block the input signal or the desired separated signal related to the detected residual separated signal by the cutoff device. This is particularly effective in a configuration in which the demultiplexer 20 is located on the second side of the cutoff device 30. This configuration example is common to the first embodiment of the optical distribution system 10 (optical distribution system 10a) described above.

[0313] [Second embodiment] 71 is a diagram showing an example of a system configuration of a second embodiment (light sorting system 10b) of the light sorting system 10 of the present invention. The light sorting system 10b includes a separation system 11b and a light sorting device 40. The separation system 11b includes a separation device 20.

[0314] The demultiplexer 20 wavelength-demultiplexes an optical signal input to the demultiplexer 20 into a desired demultiplexed signal and a residual demultiplexed signal. The demultiplexed desired demultiplexed signal is output to a path corresponding to its destination. The demultiplexer 20 detects the optical intensity of the demultiplexed residual demultiplexed signal. When the demultiplexer 20 detects that the residual demultiplexed signal has an optical intensity equal to or greater than a predetermined level, the demultiplexer 20 sends a predetermined notification to a predetermined device. The demultiplexer 21 of the demultiplexer 20 in the second embodiment may be configured similarly to the demultiplexer 21 of the demultiplexer 20 in the first embodiment. That is, the demultiplexer 21 of the demultiplexer 20 in the second embodiment may have any of the configurations shown in FIGS. 27 to 55, 59, 60, and 62 to 70.

[0315] The optical distribution device 40 distributes optical signals input to the device itself, and outputs the signals from a port according to the destination (to a path to which the destination device is connected).

[0316] 72 is a diagram showing a first specific example of the configuration of the demultiplexing system 11b. The demultiplexing device 20 in the first specific example includes a demultiplexing unit 21 and a detecting unit 22. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 10b into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0317] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal with an optical intensity equal to or greater than a predetermined intensity, the detector 22 issues a predetermined notification to a predetermined device. For example, the notification may be made by transmitting a predetermined notification signal. More specifically, the detector 22 may issue the notification to the user device, or may issue the notification to the user device via a separately provided controller.

[0318] The content of the notification may be an instruction to stop transmission, an instruction to correct the wavelength (for example, it may further include information indicating the wavelength of the correct desired signal), or an instruction to initialize. If the notification is an instruction to initialize, it may further include an instruction to correct the non-conforming state during initialization. The detector 22 may be configured to be non-reflective. In this case, the detector 22 may record information (log) indicating that it has detected the residual separated signal at a predetermined optical intensity or above and notified the detection.

[0319] In the separation system 11b shown in FIG. 72, the presence or absence of a residual signal is detected, rather than the intensity ratio between the desired signal and the residual signal. In other words, the presence or absence of a residual signal is detected based on whether the intensity of the residual signal (actually the residual separated signal) exceeds a threshold. Therefore, even if a configuration exists that detects the intensity ratio between the desired signal and the residual signal, the sensitivity can be further improved compared to such a configuration. Furthermore, it is also possible to implement the detection unit 22 using a detector with low sensitivity. In the separation system 11b shown in FIG. 72, only the desired separated signal can be output.

[0320] A second specific example of the configuration of the demultiplexing system 11b will be described. The demultiplexing device 20 in the second specific example includes a demultiplexing unit 21, a detecting unit 22, and an isolator 23. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 10b into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side. The residual demultiplexed signal is input to the isolator 23.

[0321] The isolator 23 passes the optical signal flowing from the separation unit 21 to the detection unit 22 and blocks the optical signal flowing from the detection unit 22 to the separation unit 21. The detection unit 22 receives the residual separated signal via the isolator 23. The detection unit 22 detects the optical intensity of the input residual separated signal. When the detection unit 22 detects the residual separated signal at a predetermined optical intensity or higher, it issues a predetermined notification to a predetermined device. For example, the notification may be made by transmitting a predetermined notification signal. In this case, the detection unit 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detection unit 22 may be configured to be non-reflective.

[0322] 73 is a diagram showing a third specific example of the configuration of the demultiplexing system 11b. The demultiplexing device 20 in the third specific example includes a plurality of demultiplexing units 21 and a detecting unit 22. The demultiplexing units 21 may be configured using, for example, a BDF. Each demultiplexing unit 21 receives one of the plurality of optical signals input to the optical distribution system 10b. Each demultiplexing unit 21 wavelength-demultiplexes the input optical signal into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0323] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it issues a predetermined notification to a predetermined device. For example, the notification may be made by transmitting a predetermined notification signal. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0324] We will now explain specific examples of the positional relationship of each device in the second embodiment (optical distribution system 10b) of the optical distribution system 10. In all specific examples, we will explain an example in which the optical distribution device 40 is installed in a central office, but as with the first embodiment, it may also be installed in other locations.

[0325] For example, the demultiplexer 20 may be installed at the location shown in Figures 9, 10, and 15. That is, the demultiplexer 20 may be installed on the second side at a location different from the optical distribution device 40 (a location other than a central office). For example, the demultiplexer 20 may be installed at the same location as the user equipment (e.g., in a user's premises). In this case, the optical signal transmitted from the user equipment is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. The optical distribution device 40 inputs the desired demultiplexed signal and outputs the desired demultiplexed signal from a port on the first side. Note that although a blocking device 30 is also installed in Figures 9, 10, and 15, the blocking device 30 is not necessary in the second embodiment.

[0326] For example, the demultiplexer 20 may be installed at the location shown in FIGS. 11, 12, and 16. That is, the demultiplexer 20 may be installed within the add-on package 41. In this case, the optical signal transmitted from the user device is first input to the optical distribution device 40. In this particular case, the optical signal is input to the upper left port. The optical distribution device 40 then inputs the input optical signal to the add-on package 41. The optical signal input to the add-on package 41 is then input to the demultiplexer 20 installed in the add-on package 41. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. The desired demultiplexed signal output from the add-on package 41, which has the function of the demultiplexer 20, is input to the optical distribution device 40. The optical distribution device 40 then outputs the desired demultiplexed signal from the first port. Note that although a cut-off device 30 is also installed in FIGS. 11, 12, and 16, the cut-off device 30 is not required in the second embodiment.

[0327] For example, the demultiplexer 20 may be installed at the location shown in Figures 13 and 17. That is, the demultiplexer 20 may be installed on the second side in the same location (e.g., a central office) as the optical distribution device 40. In this case, the optical signal transmitted from the user equipment is first input to the demultiplexer 20. The demultiplexer 20 outputs a desired demultiplexed signal to the optical distribution device 40. The optical distribution device 40 inputs the desired demultiplexed signal and outputs the desired demultiplexed signal from a port on the first side. Note that although a blocking device 30 is also installed in Figures 13 and 17, the blocking device 30 is not necessary in the second embodiment.

[0328] For example, the demultiplexer 20 may be installed at the position shown in Figures 14 and 18. That is, the demultiplexer 20 may be installed on the first side in the same location (e.g., a central office) as the optical distribution device 40. In this case, an optical signal transmitted from a user device is first input to the optical distribution device 40. The optical signal output from the port corresponding to the destination in the optical distribution device 40 is then input to the demultiplexer 20. The demultiplexer 20 outputs the desired demultiplexed signal to the first side. Note that although a cut-off device 30 is also installed in Figures 14 and 18, the cut-off device 30 is not necessary in the second embodiment.

[0329] [Third embodiment] 74 is a diagram showing an example of a system configuration of a third embodiment (light sorting system 10c) of the light sorting system 10 of the present invention. The light sorting system 10c includes a separation system 11c and a light sorting device 40. The separation system 11c includes a separation device 20.

[0330] The demultiplexer 20 wavelength-demultiplexes an optical signal input to the demultiplexer 20 into a desired demultiplexed signal and a residual demultiplexed signal. The demultiplexed desired demultiplexed signal is output to a path corresponding to its destination. The demultiplexer 20 detects the optical intensity of the demultiplexed residual demultiplexed signal. When the demultiplexer 20 detects that the residual demultiplexed signal has an optical intensity equal to or greater than a predetermined level, the demultiplexer 20 notifies a predetermined device of the detection result. The demultiplexer 21 of the demultiplexer 20 in the third embodiment may be configured similarly to the demultiplexer 21 of the demultiplexer 20 in the first embodiment. That is, the demultiplexer 21 of the demultiplexer 20 in the third embodiment may have any of the configurations shown in FIGS. 27 to 37, 39 to 55, and 68 to 70.

[0331] The optical distribution device 40 distributes optical signals input to the device itself, and outputs the signals from a port according to the destination (to a path to which the destination device is connected).

[0332] A first specific example of the configuration of separation system 11c will be described. The first specific example of the configuration of separation system 11c is similar to the configuration in Fig. 72. In Fig. 72, a notification signal is output from detection unit 22, but in the first specific example of the configuration of separation system 11c, a detection result is output from detection unit 22. A specific description will be given below.

[0333] The demultiplexing device 20 in the first specific example includes a demultiplexing unit 21 and a detecting unit 22. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 10c into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0334] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it notifies a predetermined device of the detection result. For example, the notification may be made by transmitting a predetermined notification signal including the detection result. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher.

[0335] In the above-described separation system 11c, the presence or absence of the intensity of the residual signal is detected, rather than the ratio of the intensities of the desired signal and the residual signal. In other words, the presence or absence of the residual signal is detected based on whether the intensity of the residual separated signal exceeds a threshold. Therefore, sensitivity can be further improved compared to a configuration that detects the ratio of the intensities of the desired separated signal and the residual separated signal. It is also possible to implement the detection unit 22 using a detector with low sensitivity. In the above-described separation system 11c, only the desired separated signal can be output.

[0336] A second specific example of the configuration of the demultiplexing system 11c will be described. The demultiplexing device 20 in the second specific example includes a demultiplexing unit 21, a detecting unit 22, and an isolator 23. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 10c into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side. The residual demultiplexed signal is input to the isolator 23.

[0337] The isolator 23 passes the optical signal flowing from the separation unit 21 to the detection unit 22 and blocks the optical signal flowing from the detection unit 22 to the separation unit 21. The detection unit 22 receives the residual separated signal via the isolator 23. The detection unit 22 detects the optical intensity of the input residual separated signal. When the detection unit 22 detects the residual separated signal at a predetermined optical intensity or higher, it notifies a predetermined device of the detection result. In this case, the detection unit 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher.

[0338] A third specific example of the configuration of separation system 11c will be described. The third specific example of the configuration of separation system 11c is similar to the configuration in Fig. 73. In Fig. 73, a notification signal is output from detection unit 22, but in the third specific example of the configuration of separation system 11c, a detection result is output from detection unit 22. A specific description will be given below.

[0339] The demultiplexing device 20 in the third specific example includes a plurality of demultiplexing units 21 and a detecting unit 22. The demultiplexing units 21 may be configured using, for example, a BDF. Each demultiplexing unit 21 receives one of the plurality of optical signals input to the optical distribution system 10c. Each demultiplexing unit 21 wavelength-demultiplexes the input optical signal into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0340] The detector 22 detects the optical intensity of the separated residual separated signal. When the detector 22 detects the residual separated signal at a predetermined optical intensity or higher, it notifies a predetermined device of the detection result. In this case, the detector 22 may record information (log) indicating that the residual separated signal has been detected at a predetermined optical intensity or higher. The detector 22 may be configured to be non-reflective.

[0341] The positional relationship between the devices in the third embodiment of the light sorting system 10 (light sorting system 10c) may be configured in the same way as in the second embodiment.

[0342] [Fourth embodiment] 75 is a diagram showing an example of a system configuration of a fourth embodiment (light sorting system 10d) of the light sorting system 10 of the present invention. The light sorting system 10d includes a separation system 11d and a light sorting device 40. The separation system 11d includes a separation device 20.

[0343] The demultiplexer 20 wavelength-demultiplexes an optical signal input to the demultiplexer 20 into a desired demultiplexed signal and a residual demultiplexed signal. The demultiplexed desired demultiplexed signal is output to a path corresponding to its destination. The demultiplexer 20 discards the separated residual demultiplexed signal. The demultiplexing unit 21 of the demultiplexer 20 in the fourth embodiment may be configured similarly to the demultiplexing unit 21 of the demultiplexer 20 in the first embodiment. That is, the demultiplexing unit 21 of the demultiplexer 20 in the fourth embodiment may have any of the configurations shown in FIGS. 27 to 37, 39 to 55, and 68 to 70. Note that in these figures, the residual demultiplexed signal is output to the detecting unit 22, but in the demultiplexer 20 in the fourth embodiment, the residual demultiplexed signal is output to the discarding unit 24 instead of the detecting unit 22.

[0344] The optical distribution device 40 distributes optical signals input to the device itself, and outputs the signals from a port according to the destination (to a path to which the destination device is connected).

[0345] 76 is a diagram showing a first specific example of the configuration of a demultiplexing system 11d. The demultiplexing device 20 in the first specific example includes a demultiplexing unit 21 and a discarding unit 24. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 10d into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0346] The discard unit 24 discards the separated residual demultiplexed signal. In other words, the discard unit 24 processes the separated residual demultiplexed signal so that it does not get mixed into the desired demultiplexed signal. The discard unit 24 may be configured as, for example, a non-reflective termination. The discard unit 24 may be configured using, for example, an isolator that passes the optical signal only in the direction from the demultiplexer 21 to the discard unit 24.

[0347] A second specific example of the configuration of the demultiplexing system 11d will be described. The demultiplexing device 20 in the second specific example includes a demultiplexing unit 21, a discarding unit 24, and an isolator 23. The demultiplexing unit 21 may be configured using, for example, a BDF. The demultiplexing unit 21 wavelength-demultiplexes an optical signal input to the optical distribution system 11d into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side. The residual demultiplexed signal is input to the isolator 23.

[0348] The isolator 23 passes the optical signal flowing from the separation unit 21 to the discard unit 24 and blocks the optical signal flowing from the discard unit 24 to the separation unit 21. The discard unit 24 receives the residual separated signal via the isolator 23. The discard unit 24 is configured using, for example, a non-reflective termination. The discard unit 24 discards the input residual separated signal.

[0349] 77 is a diagram showing a third specific example of the configuration of the demultiplexing system 11d. The demultiplexing device 20 in the third specific example includes a plurality of demultiplexing units 21 and a discarding unit 24. The demultiplexing units 21 may be configured using, for example, a BDF. Each demultiplexing unit 21 receives one of the plurality of optical signals input to the optical distribution system 10d. Each demultiplexing unit 21 wavelength-demultiplexes the input optical signal into a desired demultiplexed signal and a residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0350] The discard unit 24 discards the remaining separated signal. The discard unit 24 may be configured as, for example, a non-reflective termination. The discard unit 24 may be configured using, for example, an isolator that passes the optical signal only in the direction from the demultiplexer 21 to the discard unit 24.

[0351] The positional relationship between the devices in the fourth embodiment of the light sorting system 10 (light sorting system 10d) may be configured in the same way as in the second embodiment.

[0352] [Multiple-port variant of the second embodiment] 78 is a diagram showing a modified example of the second embodiment of the demultiplexing system 11b. The demultiplexing unit 21 may be configured using, for example, an AWG. One of the multiple optical signals input to the optical distribution system 10b is input to each input port of the demultiplexing unit 21. The demultiplexing unit 21 performs a demultiplexing process to wavelength-separate the desired signal from the residual signal from the multiple input optical signals, thereby demultiplexing the desired demultiplexed signal from the residual demultiplexed signal. The separated desired demultiplexed signal is output to the first side.

[0353] The detector 22 detects the optical intensity of the separated residual separated signals. When the detector 22 detects any of the residual separated signals with an optical intensity equal to or greater than a predetermined intensity, the detector 22 issues a predetermined notification to a predetermined device. For example, the notification may be made by transmitting a predetermined notification signal. More specifically, the detector 22 may issue the notification to the user device, or may issue the notification to the user device via a separately provided controller. The content of the notification is the same as in the second embodiment, and therefore will not be described here.

[0354] [Multiple-port variant of the third embodiment] A separation unit 21 having multiple input ports may be applied to the separation system 11c of the third embodiment. In this case, the configuration will be similar to that shown in FIG. 78. In the third embodiment, when the detection unit 22 detects a residual separated signal with a predetermined light intensity or higher, it notifies a predetermined device of the detection result. In this respect, it differs from the configuration shown in FIG. 78. Therefore, other explanations of the third embodiment will be omitted.

[0355] [Multiple-port modification of the fourth embodiment] FIG. 79 is a diagram showing a modified example of the fourth embodiment of the demultiplexing system 11d. The demultiplexing unit 21 may be configured using, for example, an AWG. One of the multiple optical signals input to the optical distribution system 10d is input to each input port of the demultiplexing unit 21. The demultiplexing unit 21 separates the desired demultiplexed signal from the residual demultiplexed signal by performing a demultiplexing process to wavelength-separate the desired signal from the residual demultiplexed signal from the multiple input optical signals. The separated desired demultiplexed signal is output to the first side. The discarding unit 24 in FIG. 79 has the same configuration as the discarding unit 24 of the fourth embodiment described above.

[0356] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0357] The present invention is applicable to optical communications. [Explanation of symbols]

[0358] 10...optical distribution system, 11...separation system, 20...separation device, 21...separation section, 22...detection section, 23...isolator, 30...interruption device, 40...optical distribution device, 211...circulator, 212...FBG, 213...directional coupler, 214...TFF, 215...AWG, 216...multiplexing section, 217...reflection section, 218...waveguide-type ring resonator, 219...lattice-type optical filter, 2110...PBS, 91...optical fuse, 92...optical monitor

Claims

1. a separation unit that separates an input optical signal into a first signal having a first wavelength and a second signal having a second wavelength that is a wavelength other than the first wavelength; a detection unit that detects the intensity of the second signal; Equipped with The separation system further comprises a blocking unit that blocks the input optical signal or the first signal when the detection unit detects the second signal at a predetermined intensity or greater.

2. a separation unit that separates an input optical signal into a first signal having a first wavelength and a second signal having a second wavelength that is a wavelength other than the first wavelength; a detection unit that detects the intensity of the second signal; Equipped with a second detection unit that detects the intensity of the input optical signal or the separated first signal; The separation system further includes a blocking unit that blocks the input optical signal or the first signal when the second detection unit detects the input optical signal at a predetermined intensity or greater.

3. a separation unit that separates an input optical signal into a first signal having a first wavelength and a second signal having a second wavelength that is a wavelength other than the first wavelength; a detection unit that detects the intensity of the second signal; Equipped with The separation unit further includes a multiplexing unit that inputs, multiplexes, and outputs at least one of a plurality of first signals connected to a device different from the detection unit or the discard unit that discards the signals, or a plurality of second signals connected to the detection unit or the discard unit.

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