Optical transceiver
An optical transceiver consisting of a pseudo-random code generator and related processing units solves the high-resolution problem of optical loss and radiation distribution measurement in existing technologies, and realizes high-precision detection of optical loss and radiation distribution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MITSUBISHI ELECTRIC CORP
- Filing Date
- 2023-11-02
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are insufficient for measuring optical loss and radiation distribution at high distance resolution, and the dynamic range of the measurement distance decreases and fiber loss increases when the resolution is increased.
By employing a pseudo-random code generator, a digital optical transmitter, an analog optical receiver, a correlation processing unit, a differential processing unit, and a differential calculation unit, loss curves and differential data are calculated through correlation processing of the pseudo-random code signal and the received signal, thereby achieving high-distance resolution optical loss measurement.
It achieves high-resolution measurement of optical loss and radiation distribution, accurately detects increases in local radiation, and is unaffected by optical device degradation.
Smart Images
Figure CN122122479A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to an optical transceiver capable of measuring optical loss. Background Technology
[0002] Previously, there were known devices for obtaining radiation distribution information (for example, see Patent Document 1). In the device disclosed in Patent Document 1, in order to obtain radiation distribution information along the optical fiber used for the sensor, a single-pulse OTDR measurement method driven by a light source with a pulse width of tw and a pulse period of tp was used.
[0003] This method performs OTDR processing on multiple wavelengths, including Stokes light and anti-Stokes light, and also estimates the radiation exposure by utilizing the wavelength dependence (differential) of the degradation caused by radiation. Additionally, Patent Document 1 also describes an OTDR measurement method using a pseudo-random pulse mode driven by a pulse train.
[0004] Existing technical documents
[0005] Patent documents
[0006] Patent Document 1: Japanese Patent Application Publication No. 04-274787 Summary of the Invention
[0007] The problem the invention aims to solve
[0008] However, the existing method disclosed in Patent Document 1 is difficult to perform high-resolution measurements of radiation distribution. Furthermore, not only is high-resolution measurement of radiation distribution difficult, but also high-resolution measurement of optical loss is challenging.
[0009] Furthermore, in conventional methods, if the OTDR transmit light is pulsed narrowly to achieve higher resolution, the backscattering power decreases. Consequently, the dynamic range of the measurement distance is reduced, and fiber loss increases in radiation environments, making it difficult to maintain the measurement range.
[0010] This disclosure was made to solve the aforementioned problems, and its purpose is to provide an optical transceiver that can measure optical loss at high distance resolution compared to the past.
[0011] means for solving problems
[0012] The optical transceiver disclosed herein is characterized by comprising: a pseudo-random code generator that outputs a signal representing a pseudo-random code; a digital optical transmitter that generates and transmits transmit light based on the signal representing the pseudo-random code output by the pseudo-random code generator, capable of transmitting at a speed of 1 Gbit or more; an analog optical receiver that receives input light as receive light and converts the received light into a receive signal; a transceiver switch that outputs the transmit light transmitted by the digital optical transmitter to one end of an optical fiber and outputs the light from the optical fiber to the analog optical receiver; and an analog-to-digital converter that converts the received light based on the receive signal obtained from the analog optical receiver into a receive signal. The signal is converted from an analog signal to a digital signal; the correlation processing unit performs correlation processing on the signal representing the pseudo-random code output by the pseudo-random code generator and the received signal obtained by the analog-to-digital converter, thereby calculating loss curve data; the differential processing unit performs differential processing on the loss curve data calculated by the correlation processing unit, thereby calculating loss curve differential data; and the differential calculation unit calculates the difference between the loss differential data and the loss curve differential data based on the loss differential data before fiber installation and the loss curve differential data calculated by the differential processing unit.
[0013] The effects of the invention
[0014] According to this disclosure, due to the configuration as described above, optical loss can be measured with high distance resolution compared to the past. Attached Figure Description
[0015] Figure 1 This is a block diagram illustrating a structural example of the optical transceiver of Embodiment 1.
[0016] Figure 2 This is a flowchart illustrating an example of the operation of the optical transceiver in Embodiment 1.
[0017] Figure 3 This is a diagram illustrating an example of loss data and loss curve data processed in the optical transceiver of Embodiment 1.
[0018] Figure 4 This is a diagram illustrating an example of loss differential data, loss curve differential data, and absorption line accumulation distribution processed in the optical transceiver of Embodiment 1.
[0019] Figure 5 This is a block diagram illustrating a structural example of the optical transceiver of Embodiment 2.
[0020] Figure 6 This is a block diagram illustrating a structural example of the receiving side of the digital optical transceiver in Embodiment 2.
[0021] Figure 7This is a graph illustrating the gain of the LA in the optical transceiver of Embodiment 2 (using leaked light).
[0022] Figure 8 This is a graph illustrating the gain of the LA in the optical transceiver of Embodiment 2 (in the case of low or no leakage light).
[0023] Figure 9 This is a block diagram illustrating a structural example of the optical transceiver system of Embodiment 3.
[0024] Figure 10 This is a block diagram illustrating another structural example of the optical transceiver system of Embodiment 3.
[0025] Figure 11 This is a block diagram illustrating a structural example of the optical transceiver system of Embodiment 4.
[0026] Figure 12 This is a flowchart illustrating an example of the operation of the optical transceiver system in Embodiment 4.
[0027] Figure 13 This is a diagram illustrating an example of loss data and loss curve data processed in the first and second optical transceivers of Embodiment 4.
[0028] Figure 14 This is a diagram illustrating an example of loss differential data, loss curve differential data, and absorption line accumulation distribution processed in the first and second optical transceivers of Embodiment 4.
[0029] Figure 15 This is a diagram showing an example of the cumulative absorption line distribution after the optical transceivers of Embodiment 4 are combined.
[0030] Figure 16A , Figure 16B This is a block diagram illustrating an example of the hardware structure of the optical transceiver in embodiments 1 to 4. Detailed Implementation
[0031] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings.
[0032] Implementation method 1.
[0033] Figure 1 This is a diagram illustrating a structural example of the optical transceiver 1 according to Embodiment 1. Figure 1 In the example shown, optical transceiver 1 is a fiber optic radiation distribution meter that measures the cumulative distribution of absorption lines (radiation line distribution). Additionally, in... Figure 1 The example illustrates a case where optical fiber 2 is mounted on the object being measured via an adhesive unit and exposed to radiation. Figure 1 In the image, the multiple arrows shown on the upper side of fiber 2 indicate the illumination of radiation.
[0034] Furthermore, this optical transceiver 1 can be applied to power plants such as satellites and nuclear reactors. For example, even when the optical transceiver 1 is applied to a location that is inaccessible to humans, such as a nuclear reactor, the optical transceiver 1 can remotely measure the distribution of the cumulative absorption line.
[0035] like Figure 1 As shown, the optical transceiver 1 includes a pseudo-random code generator 101, a digital optical transmitter 102, an optical circulator (transceiver switcher) 103, an analog optical receiver 104, an ADC (analog-to-digital converter) 105, a correlation processing unit 106, a differential processing unit 107, a differential data acquisition unit 108, and a differential calculation unit 109. The optical transceiver 1 is disposed at one end of the optical fiber 2.
[0036] The pseudo-random code generator 101 generates pseudo-random codes. That is, the pseudo-random code generator 101 generates codes that are randomly arranged from "0" or "1".
[0037] The signal indicating the pseudo-random code generated by the pseudo-random code generator 101 is output to the digital optical transmitter 102 and the related processing unit 106.
[0038] Digital optical transmitter 102 generates transmit light based on a signal representing a pseudo-random code output by pseudo-random code generator 101, and sends the transmit light to optical circulator 103. The transmit light generated by digital optical transmitter 102 is continuous light.
[0039] The digital optical transmitter 102 is a digital optical transmitter capable of transmitting more than 1 Gbit.
[0040] For example, an SFP (Small Form-factor Pluggable) module can be used as the digital optical transmitter 102. Furthermore, the digital optical transmitter 102 is not limited to SFP; for example, higher-speed modules such as SFP+, QSFP, and SFP28 can also be used, as long as it is a digital optical transmitter that performs OOK (On-Off-Keying) digital modulation.
[0041] The optical circulator 103 outputs the transmit light sent by the digital optical transmitter 102 to one end of the optical fiber 2.
[0042] In addition, the optical circulator 103 outputs the light (backscattered light) from the optical fiber 2 to the analog optical receiver 104.
[0043] In addition, Figure 1 The example shown illustrates the use of an optical circulator 103 as a transceiver switcher. However, the transceiver switcher is not limited to this; for example, an optical coupler can also be used as a transceiver switcher.
[0044] Analog optical receiver 104 receives light from optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by analog optical receiver 104 is an analog signal. The received signal obtained by analog optical receiver 104 is output to ADC 105.
[0045] As the analog optical receiver 104, a PD (photodiode) can be used, for example.
[0046] The ADC105 converts the received signal from the analog optical receiver 104 into a digital signal. The received signal, which is a digital signal, obtained by the ADC105 is output to the correlation processing unit 106.
[0047] In addition, in order to improve the SNR of the received signal, the ADC105 can also acquire the received signal multiple times and perform averaging on the multiple received signals, thereby obtaining the received signal output to the correlation processing unit 106.
[0048] The correlation processing unit 106 performs correlation processing on the signal representing the pseudo-random code output by the pseudo-random code generator 101 and the received signal obtained by the ADC 105, thereby calculating loss curve data. This loss curve data represents the optical loss along the distance direction of the optical fiber 2. The calculation of the loss curve data performed by the correlation processing unit 106 can be performed using conventionally known calculation methods, and its explanation is omitted. The loss curve data calculated by the correlation processing unit 106 is output to the differential processing unit 107.
[0049] The differential processing unit 107 performs differential processing based on the loss curve data calculated by the correlation processing unit 106, thereby calculating the differential data of the loss curve. This differential data of the loss curve represents the rate of change of optical loss along the distance direction of the optical fiber 2. The differential data of the loss curve calculated by the differential processing unit 107 is output to the differential calculation unit 109.
[0050] The differential data acquisition unit 108 acquires the differential loss data before the optical fiber 2 is installed. Furthermore, the differential loss data represents the rate of change of optical loss along the distance direction of the optical fiber 2 before it is placed in a radiation environment, and is measured beforehand. The differential loss data acquired by the differential data acquisition unit 108 is output to the differential calculation unit 109.
[0051] The differential calculation unit 109 calculates the difference between the loss differential data acquired by the differential data acquisition unit 108 and the loss curve differential data calculated by the differential processing unit 107. This difference represents the optical loss per unit length along the distance direction of the optical fiber 2.
[0052] Furthermore, when the optical transceiver 1 functions as a fiber optic radiation distribution meter, the differential calculation unit 109 calculates the cumulative absorption line distribution based on the differential calculated above. This cumulative absorption line distribution represents the distribution of radiation along the distance direction of the optical fiber 2.
[0053] Next, refer to Figure 2 right Figure 1 An example of the operation of the optical transceiver 1 in Embodiment 1 will be described. Specifically, an example of the operation of the optical transceiver 1 when it functions as a fiber optic radiation distribution meter will be shown below.
[0054] exist Figure 1 In the example of the operation of the optical transceiver 1 in Embodiment 1 shown, for example, as Figure 2 As shown, firstly, the pseudo-random code generator 101 generates a pseudo-random code (step ST101). The signal representing the pseudo-random code generated by the pseudo-random code generator 101 is output to the digital optical transmitter 102 and the correlation processing unit 106.
[0055] Next, the digital optical transmitter 102 generates transmit light based on the signal representing the pseudo-random code output by the pseudo-random code generator 101 and sends it to the optical circulator 103, which outputs the transmit light to one end of the optical fiber 2 (step ST102).
[0056] Next, the optical circulator 103 outputs the light (backscattered light) from the optical fiber 2 to the analog optical receiver 104, which receives the light as the received light and converts it into a received signal (step ST103). The received signal obtained by the analog optical receiver 104 is output to the ADC 105.
[0057] Next, the ADC105 converts the received signal obtained by the analog optical receiver 104 from an analog signal into a digital signal (step ST104). The received signal obtained by the ADC105 as a digital signal is output to the correlation processing unit 106.
[0058] Next, the correlation processing unit 106 performs correlation processing on the signal representing the pseudo-random code output by the pseudo-random code generator 101 and the received signal obtained by the ADC 105, thereby calculating loss curve data (step ST105). The loss curve data calculated by the correlation processing unit 106 is output to the differential processing unit 107.
[0059] Next, the differential processing unit 107 performs differential processing based on the loss curve data calculated by the correlation processing unit 106, thereby calculating the differential data of the loss curve (step ST106). The differential data of the loss curve calculated by the differential processing unit 107 is output to the differential calculation unit 109.
[0060] In addition, the differential data acquisition unit 108 acquires the loss differential data before the fiber 2 is installed (step ST107). The loss differential data acquired by the differential data acquisition unit 108 is output to the differential calculation unit 109.
[0061] Next, the difference calculation unit 109 calculates the difference between the loss differential data and the loss curve differential data based on the loss differential data obtained by the differential data acquisition unit 108 and the loss curve differential data calculated by the differential processing unit 107, and calculates the distribution of the cumulative amount of absorption line (step ST108).
[0062] Figure 3 An example of loss data and loss curve data processed in the optical transceiver 1 of Embodiment 1 is shown.
[0063] exist Figure 3 In the diagram, label 31 represents the loss data (Lo(x)) before fiber 2 is installed, label 32 represents the loss curve data (L(x)), and label 33 represents the loss curve data (L(x)) under conditions of optical device (digital optical transmitter 102 and analog optical receiver 104) degradation. Additionally, in Figure 3 In the example, the area indicated by label 34 is the area where the optical power is significantly reduced, and it is the area that is irradiated in large quantities.
[0064] Such as Figure 3 As shown, in the loss curve data with the presence of optical device degradation shown in label 33, compared with the loss curve data without optical device degradation shown in label 32, the overall optical power decreases as the optical device deteriorates.
[0065] Figure 4 An example is shown of loss differential data, loss curve differential data, and absorption line cumulative distribution processed in the optical transceiver 1 of Embodiment 1.
[0066] exist Figure 4 In the diagram, label 41 represents the loss differential data ({Lo(x)}') before fiber 2 is installed, label 42 represents the loss curve differential data ({L(x)}'), and label 43 represents the loss curve differential data ({L(x)}') under conditions of optical device degradation. Additionally, in... Figure 4 In the example, the part indicated by label 44 is the part where the power is significantly reduced and is the part that is irradiated in large quantities.
[0067] In addition, such as Figure 4 As shown, the cumulative absorption line distribution is E(x) = S{Lo(x) - L(x)}'. Furthermore, S is a coefficient ([Gy / (dB / m)]) that shows the relationship between the degradation of the optical fiber 2 used for the sensor and the amount of radiation, and is measured beforehand.
[0068] Such as Figure 4 As shown, in the differential data of the loss curve with the presence of optical device degradation shown in label 43, there is no change compared to the differential data of the loss curve without the presence of optical device degradation shown in label 42, which is unrelated to the degradation of the optical device.
[0069] Thus, in the optical transceiver 1 of Embodiment 1, by taking the difference between the differential loss data before the fiber 2 is installed and the differential loss curve data, the optical loss and radiation distribution can be measured without being affected by the degradation of the optical device caused by radiation. That is, in the optical transceiver 1 of Embodiment 1, by taking the difference between the differential loss data before the fiber 2 is installed and the differential loss curve data, the measurement results of optical loss and radiation do not change based on whether or not there is degradation of the optical device.
[0070] Furthermore, in the existing technology, the resolution is limited by the size of the optical fiber 2 and the pulse width of the transmitted light.
[0071] In contrast, in the optical transceiver 1 of Embodiment 1, high-resolution data corresponding to the bit rate of the digital optical transmitter 102 is obtained. Therefore, in the optical transceiver 1 of Embodiment 1, local increases in radiation can be detected through differential processing.
[0072] As described above, according to this embodiment 1, the optical transceiver 1 includes: a pseudo-random code generator 101 that outputs a signal representing a pseudo-random code; a digital optical transmitter 102 that generates and transmits transmit light based on the signal representing the pseudo-random code output by the pseudo-random code generator 101, capable of transmitting at least 1 Gbit; an analog optical receiver 104 that receives input light as receive light and converts the received light into a receive signal; a transceiver switch that outputs the transmit light transmitted by the digital optical transmitter 102 to one end of the optical fiber 2 and outputs the light from the optical fiber 2 to the analog optical receiver 104; and an ADC 105 that, based on the receive signal obtained from the analog optical receiver 104, converts... The received signal is converted from an analog signal to a digital signal; the correlation processing unit 106 performs correlation processing on the signal representing the pseudo-random code output by the pseudo-random code generator 101 and the received signal obtained by the ADC 105, thereby calculating loss curve data; the differential processing unit 107 performs differential processing on the loss curve data calculated by the correlation processing unit 106, thereby calculating loss curve differential data; and the differential calculation unit 109 calculates the difference between the loss differential data and the loss curve differential data based on the loss differential data before the fiber 2 is installed and the loss curve differential data calculated by the differential processing unit 107.
[0073] Furthermore, according to Embodiment 1, the digital optical transmitter 102 is a digital optical transmitter that performs OOK modulation.
[0074] Therefore, compared with the conventional method, the optical transceiver 1 of Embodiment 1 can measure optical loss with high distance resolution.
[0075] Furthermore, according to this embodiment 1, the differential calculation unit 109 can also calculate the cumulative absorption line distribution based on the calculated difference. Therefore, compared to the conventional method, the optical transceiver 1 of embodiment 1 can measure the radiation line distribution with high distance resolution.
[0076] Implementation method 2.
[0077] Figure 5 This is a diagram showing a structural example of the optical transceiver 1 in Embodiment 2. Figure 5 The optical transceiver 1 of Embodiment 2 shown is relative to Figure 1 The optical transceiver 1 shown in Embodiment 1 comprises a digital optical transmitter 102 and an analog optical receiver 104, all of which are composed of a digital optical transceiver 110. Figure 5 The other structural examples in the optical transceiver 1 of Embodiment 2 shown are the same as those in the optical transceiver 1 of Embodiment 1, and are labeled with the same reference numerals. Only the different parts are described.
[0078] The transmitting side of the digital optical transceiver 110 generates transmit light based on a signal representing a pseudo-random code output by the pseudo-random code generator 101, and outputs the transmit light to the optical circulator 103.
[0079] The receiving side of the digital optical transceiver 110 receives light (backscattered light and leakage light) from the optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by the receiving side of the digital optical transceiver 110 is output to the ADC 105. In addition, the receiving side of the digital optical transceiver 110 uses the leakage light from the optical circulator 103 to fix the gain of the LA 1043 (described later).
[0080] The digital optical transceiver 110 is a digital optical transceiver capable of transmitting more than 1 Gbit.
[0081] As the digital optical transceiver 110, for example, an SFP transmit port and receive port can be used. Furthermore, the digital optical transceiver 110 is not limited to SFP; higher-speed modules such as SFP+, QSFP, and SFP28 can also be used, as long as it is a digital optical transceiver performing OOK digital modulation. For example, a PAM4 (4 Pulse Amplitude Modulation) digital optical transceiver can be used as the digital optical transceiver 110.
[0082] Additionally, the optical circulator 103 outputs the leakage light of the transmitted light sent from the transmitting side of the digital optical transceiver 110, i.e., the leakage light that can fix the gain of LA1043, to the receiving side of the digital optical transceiver 110. Furthermore, the leakage light is, for example, -20dB or higher.
[0083] In addition, for example, such as Figure 6 As shown, the receiving side of the digital optical transceiver 110 typically consists of PD1041, TIA (transimpedance amplifier) 1042 and LA (limiting amplifier) 1043.
[0084] PD1041 receives light from optical circulator 103 as received light and converts the received light into an electrical signal. The electrical signal obtained by PD1041 is output to TIA1042.
[0085] The TIA1042 converts the current of an electrical signal into a voltage based on the electrical signal converted by the PD1041. The electrical signal converted by the TIA1042 is then output to the LA1043.
[0086] The LA1043 limits the electrical signal converted by the TIA1042. The electrical signal processed by the LA1043 is then output as the received signal to the ADC105.
[0087] Here, the gain of LA1043 increases or decreases according to the average optical power, and LA1043 operates in such a way that the voltage amplitude of the input electrical signal is saturated at that gain.
[0088] In contrast, leaked light is transmitted light that has been modulated by a pseudo-random code and has been subjected to some loss, without time variation in average power.
[0089] Therefore, by inputting this leaked light into the LA1043, the gain of the LA1043 is determined based on the average power of the leaked light. As a result, the Rayleigh scattering component below the leaked light, which does not contribute significantly to the average power, is output with a roughly constant gain regardless of the detection time. Furthermore, the detection time is proportional to the distance.
[0090] For example, in Figure 7 On the left, label 71 indicates the output power of the leakage light component from TIA1042, label 72 indicates the output power of the Rayleigh scattering component from TIA1042 at a detection time of t1, and label 73 indicates the output power of the Rayleigh scattering component from TIA1042 at a detection time of t2 (≠t1). Additionally, label 74 indicates the output power of the leakage light component from LA1043, which outputs leakage light at a constant power. Furthermore, label 75 indicates the output power of the Rayleigh scattering component from LA1043 at a detection time of t1, and label 76 indicates the output power of the Rayleigh scattering component from LA1043 at a detection time of t2.
[0091] Such as Figure 7 As shown on the left, the input power of the leaked light, which is always input to the receiver side of the digital optical transceiver 110, is greater than that of the Rayleigh scattering component. Therefore, in LA1043, the gain (G) is fixed to the gain that saturates the leaked light. As a result, the Rayleigh scattering components at detection time t1 and t2 are independent of the difference in detection time and are output with a common gain (G), becoming analog values.
[0092] On the other hand, such as Figure 7 As shown on the right, in the correlation processing, the leaky light component only has a high correlation gain at the point corresponding to the most recent time (near t=0 shown in label 77). Therefore, for times when the correlation value between the leaky light component and the pseudo-random code is low, the Rayleigh scattering component can be detected, and the loss curve data can be obtained correctly.
[0093] In addition, Figure 7 On the right, label 78 indicates the noise level caused by the leaked light.
[0094] In this way, by fixing the gain of LA1043 through the leakage light component, the loss curve data can be obtained more accurately.
[0095] In contrast, in the optical transceiver 1 of Embodiment 2, the envisioned operation cannot be performed when the leakage light component is small or there is no leakage light component.
[0096] That is, such as Figure 8 As shown on the left, in the case of low or no leakage light component, in the LA1043, at detection time t1, the gain (G1) is fixed to the gain that saturates the Rayleigh scattering component at detection time t1, and at detection time t2, the gain (G2) is fixed to the gain that saturates the Rayleigh scattering component at detection time t2. In this case, as... Figure 8 As shown on the right, in the Rayleigh scattering components with a detection time of t1 and the Rayleigh scattering components with a detection time of t2, the output power is roughly the same, the loss change disappears, and the loss curve cannot be obtained correctly.
[0097] exist Figure 8 In the figure, 81 indicates the output power of the Rayleigh scattering component from LA1043 when the detection time is t1 or t2.
[0098] The operation examples other than those described above in the optical transceiver 1 of Embodiment 2 are the same as those in the optical transceiver 1 of Embodiment 1.
[0099] As described above, according to this embodiment 2, the digital optical transmitter 102 and the analog optical receiver 104 are composed of a digital optical transceiver 110. The receiving side of the digital optical transceiver 110 has an LA1043. The transceiver switch outputs the leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver 110, that is, the leakage light that can fix the gain of the LA1043, to the receiving side of the digital optical transceiver 110.
[0100] Furthermore, according to Embodiment 2, the leakage light is above -20dB.
[0101] Therefore, in addition to the effects of the optical transceiver 1 in Embodiment 1, the optical transceiver 1 in Embodiment 2 can also use an inexpensive digital optical transceiver 110 as a digital optical transmitter 102 and an analog optical receiver 104, thus enabling the optical transceiver 1 to be constructed inexpensively.
[0102] Implementation method 3.
[0103] In Embodiment 2, a case is shown where the gain of LA1043 is fixed using leaked light. In contrast, in Embodiment 3, a case is shown where the gain of LA1043 is fixed using transmit light (virtual light) sent from the optical transceiver 1 at the other end.
[0104] Figure 9 This is a diagram illustrating a structural example of the optical transceiver system of Embodiment 3.
[0105] The optical transceiver system has a pair of optical transceivers 1 (first optical transceiver 1-1 and second optical transceiver 1-2).
[0106] The first optical transceiver 1-1 and the second optical transceiver 1-2 are optical transceivers 1 with the same structure. The first optical transceiver 1-1 and the second optical transceiver 1-2 are configured opposite each other via optical fiber 2. That is, the first optical transceiver 1-1 is located at one end of optical fiber 2, and the second optical transceiver 1-2 is located at the other end of optical fiber 2. Furthermore, in... Figure 9 The detailed structural diagram of the second optical transceiver 1-2 is omitted in the text.
[0107] In Figure 9 In the optical transceiver 1 of the optical transceiver system of Embodiment 3 shown, relative to Figure 1 The optical transceiver 1 of Embodiment 1 shown comprises a digital optical transmitter 102 and an analog optical receiver 104, both composed of a digital optical transceiver 110, with the addition of a virtual code generator 111, a selector 112, and an optical power adjustment unit 113. Figure 9 Other structural examples of the optical transceiver 1 included in the optical transceiver system of Embodiment 3 shown are similar to those in Embodiment 3. Figure 1 The optical transceiver 1 shown in Embodiment 1 has the same structure as the example shown, and is labeled with the same reference numerals. Only the different parts are described.
[0108] Virtual code generator 111 generates virtual codes. The virtual codes are codes unrelated to the pseudo-random codes used in the optical transceiver 1 at the other end. A signal representing the virtual codes generated by the virtual code generator 111 is output to selector 112.
[0109] Selector 112 outputs either a signal representing a pseudo-random code from pseudo-random code generator 101 or a signal representing a virtual code from virtual code generator 111 to the transmitting side of digital optical transceiver 110.
[0110] Here, when the measurement is performed locally, selector 112 outputs the signal representing the pseudo-random code from pseudo-random code generator 101 to the transmitting side of digital optical transceiver 110. That is, in this case, selector 112 does not output the signal representing the virtual code from virtual code generator 111 to the transmitting side of digital optical transceiver 110.
[0111] On the other hand, when the optical transceiver 1 at the other end is performing measurements, the selector 112 outputs the signal representing the virtual code from the virtual code generator 111 to the transmitting side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output the signal representing the pseudo-random code from the pseudo-random code generator 101 to the transmitting side of the digital optical transceiver 110.
[0112] The transmitting side of the digital optical transceiver 110 generates transmit light based on the signal output by the selector 112 and outputs the transmit light to the optical circulator 103. Furthermore, when the digital optical transceiver 110 generates transmit light modulated using a virtual code output by the virtual code generator 111, this transmit light is also referred to as virtual light. Moreover, when the virtual code is a code consisting entirely of "1", the virtual light is called CW light.
[0113] The receiving side of the digital optical transceiver 110 receives light (backscattered light and dummy light) from the optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by the receiving side of the digital optical transceiver 110 is output to the ADC 105. In addition, the receiving side of the digital optical transceiver 110 uses the dummy light from the optical circulator 103 to fix the gain of the LA 1043.
[0114] The digital optical transceiver 110 is a digital optical transceiver capable of transmitting more than 1 Gbit.
[0115] As the digital optical transceiver 110, for example, an SFP transmit port and receive port can be used. Furthermore, the digital optical transceiver 110 is not limited to SFP; higher-speed modules such as SFP+, QSFP, and SFP28 can also be used, as long as it is a digital optical transceiver performing OOK digital modulation. For example, a PAM4 digital optical transceiver can be used as the digital optical transceiver 110.
[0116] The structure of the digital optical transceiver 110 is the same as that of the digital optical transceiver 110 shown in Embodiment 2.
[0117] The optical power adjustment unit 113 adjusts the optical power of the transmitted light on the transmitting side of the digital optical transceiver 110.
[0118] In addition, the optical power adjustment unit 113 is not a necessary structure for the optical transceiver 1, and may not be provided in the optical transceiver 1.
[0119] In addition, Figure 9 The diagram shows a case where a virtual code generator 111 for generating virtual codes is provided in the optical transceiver 1, separate from the pseudo-random code generator 101.
[0120] However, it is not limited to this; for example, it can also be as follows: Figure 10As shown, no virtual code generator 111 is provided in optical transceiver 1. In pseudo-random code generator 101, in addition to pseudo-random codes, a virtual code unrelated to the pseudo-random code in the optical transceiver 1 at the other end is generated. In this case, as... Figure 10 As shown, selector 112 is not required in optical transceiver 1.
[0121] exist Figure 10 In the configuration shown, when the measurement is performed locally, the pseudo-random code generator 101 generates a pseudo-random code and outputs a signal representing the pseudo-random code to the transmitting side of the digital optical transceiver 110. That is, in this case, the pseudo-random code generator 101 does not generate a virtual code.
[0122] On the other hand, when the optical transceiver 1 at the other end is performing measurements, the pseudo-random code generator 101 generates a virtual code and outputs a signal representing the virtual code to the transmitting side of the digital optical transceiver 110. That is, in this case, the pseudo-random code generator 101 does not generate a pseudo-random code.
[0123] Next, an operational example of the optical transceiver system in Embodiment 3 will be described. Here, the measurement of the first optical transceiver 1-1 will be described.
[0124] While the first optical transceiver 1-1 is performing measurements, the second optical transceiver 1-2 transmits virtual light to the first optical transceiver 1-1 via optical fiber 2. The virtual code that forms the basis of this virtual light is a virtual code that is unrelated to the pseudo-random code used in the first optical transceiver 1-1.
[0125] Furthermore, the first optical transceiver 1-1 uses virtual light from the second optical transceiver 1-2 to fix the gain of the LA1043 on the receiving side of its own digital optical transceiver 110. That is, in the optical transceiver system of Embodiment 3, instead of using the leakage light shown in Embodiment 2, virtual light is used to fix the gain of the LA1043.
[0126] Furthermore, if the virtual light level is too high, the noise floor becomes high after related processing, making it impossible to measure. Therefore, in such cases, the optical power adjustment unit 113 adjusts the optical power of the digital optical transceiver 110 to reduce it to a measurable level.
[0127] The operation examples other than those described above in the optical transceiver 1 of Embodiment 3 are the same as those in the optical transceiver 1 of Embodiment 1.
[0128] As described above, according to this embodiment 3, the digital optical transmitter 102 and the analog optical receiver 104 are composed of a digital optical transceiver 110. The receiving side of the digital optical transceiver 110 has an LA1043. The transceiver switch outputs the transmit light from the optical transceiver 1 located at the other end of the optical fiber 2, which is based on a virtual code unrelated to the pseudo-random code used locally, to the receiving side of the digital optical transceiver 110.
[0129] Furthermore, according to this embodiment 3, it includes: a virtual code generator 111 that outputs a signal representing a virtual code, which is unrelated to the pseudo-random code used in the optical transceiver 1 provided at the other end of the optical fiber 2; and a selector 112 that outputs either a signal representing a pseudo-random code output by the pseudo-random code generator 101 or a signal representing a virtual code output by the virtual code generator 111, wherein the transmitting side of the digital optical transceiver 110 generates and outputs transmit light based on the signal output by the selector 112.
[0130] Alternatively, according to embodiment 3, the pseudo-random code generator 101 outputs a signal representing a pseudo-random code, or a signal representing a virtual code unrelated to the pseudo-random code used in the optical transceiver 1 set at the other end of the optical fiber 2, and the transmitting side of the digital optical transceiver 110 generates and outputs transmission light based on the signal output by the pseudo-random code generator 101.
[0131] Therefore, in addition to the effects of the optical transceiver 1 of Embodiment 1, the optical transceiver 1 of Embodiment 3 can also use an inexpensive digital optical transceiver 110 as the digital optical transmitter 102 and the analog optical receiver 104, thus enabling the optical transceiver 1 to be constructed inexpensively. Furthermore, compared to the optical transceiver 1 of Embodiment 2, the optical transceiver system of Embodiment 3 can alleviate the leakage photoelectric leveling requirements in the transceiver switch and improve the level adjustment performance of the optical transceiver 1.
[0132] Implementation method 4.
[0133] Figure 11 This is a diagram illustrating a structural example of the optical transceiver system of Embodiment 4.
[0134] Figure 11 The optical transceiver 1 included in the optical transceiver system of Embodiment 4 shown is relative to Figure 9 The optical transceiver 1 of the optical transceiver system shown in Embodiment 3 has an additional communication function unit 114. Figure 11 Other structural examples of the optical transceiver 1 included in the optical transceiver system of Embodiment 4 shown are similar to those in Embodiment 4. Figure 9 The optical transceiver 1 in the optical transceiver system of Embodiment 3 shown has the same structure as the optical transceiver 1 shown, and is labeled with the same reference numerals. Only the different parts are described.
[0135] In addition, the received signal obtained by ADC105 is output to the correlation processing unit 106 and the communication function unit 114.
[0136] The communication function unit 114 outputs the calculation result of the differential calculation unit 109 as a communication signal (TX) to the selector 112.
[0137] Furthermore, the communication function unit 114 obtains the communication signal (RX) from the optical transceiver 1 at the other end from the received signal obtained by the ADC 105. Then, the communication function unit 114 outputs the obtained communication signal to the differential calculation unit 109.
[0138] In addition, selector 112 outputs the signal representing the pseudo-random code output by pseudo-random code generator 101, the signal representing the virtual code output by virtual code generator 111, or the communication signal (TX) output by communication function unit 114 to the transmitting side of digital optical transceiver 110.
[0139] Here, when the measurement is performed locally, selector 112 outputs the signal representing the pseudo-random code from pseudo-random code generator 101 to the transmitting side of digital optical transceiver 110. That is, in this case, selector 112 does not output the signal representing the virtual code from virtual code generator 111 and the communication signal (TX) from communication function unit 114 to the transmitting side of digital optical transceiver 110.
[0140] Furthermore, when the optical transceiver 1 at the other end is being measured, the selector 112 outputs the signal representing the virtual code from the virtual code generator 111 to the transmitting side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output the signal representing the pseudo-random code from the pseudo-random code generator 101 and the communication signal (TX) from the communication function unit 114 to the transmitting side of the digital optical transceiver 110.
[0141] On the other hand, when communicating with the optical transceiver 1 at the other end, the selector 112 outputs the communication signal (TX) output by the communication function unit 114 to the transmitting side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output the signal representing the pseudo-random code output by the pseudo-random code generator 101 and the signal representing the virtual code output by the virtual code generator 111 to the transmitting side of the digital optical transceiver 110.
[0142] In addition, the transmitting side of the digital optical transceiver 110 generates transmit light based on the signal output by the selector 112 and outputs the transmit light to the optical circulator 103.
[0143] In addition, the differential calculation unit 109 combines its own calculation results with the calculation results of the differential calculation unit 109 in the optical transceiver 1 at the other end, based on the communication signal (RX) obtained by the communication function unit 114.
[0144] In addition, the ADC105 can always output the received signal to the correlation processing unit 106 and the communication function unit 114, or it can switch the correlation processing unit 106 or the communication function unit 114 as the output destination according to the switching of the selector 112.
[0145] When the ADC105 switches the output destination, it outputs the received signal to the related processing unit 106 when performing measurements on the local device, and outputs the received signal to the communication function unit 114 when communicating with the optical transceiver 1 at the other end.
[0146] Next, refer to Figure 12 right Figure 11 An operational example of the optical transceiver system shown in Embodiment 4 will be described. Hereinafter, an operational example will be shown when the first optical transceiver 1-1 and the second optical transceiver 1-2 function as fiber optic radiation distribution meters.
[0147] First, an optical transceiver 1 performs a measurement of the cumulative absorption line distribution (step ST201). For example, the first optical transceiver 1-1 performs the measurement of the cumulative absorption line distribution. The measurement operation at this time is the same as that shown in Embodiment 3.
[0148] Then, another optical transceiver 1 performs a measurement of the cumulative absorption line distribution (step ST202). For example, the second optical transceiver 1-2 performs the measurement of the cumulative absorption line distribution. The measurement operation at this time is the same as that shown in Embodiment 3.
[0149] Then, after the absorption line cumulant distribution is measured in the first optical transceiver 1-1 and the second optical transceiver 1-2, one optical transceiver 1 acquires the measurement result of the other optical transceiver 1 (step ST203). For example, the first optical transceiver 1-1 acquires the measurement result of the second optical transceiver 1-2. At this time, the first optical transceiver 1-1 and the second optical transceiver 1-2 operate in communication mode. The second optical transceiver 1-2 transmits data representing its calculated absorption line cumulant distribution as a communication signal (TX), and the first optical transceiver 1-1 acquires this communication signal (TX) as a communication signal (RX). Therefore, the first optical transceiver 1-1 is able to acquire data representing the absorption line cumulant distribution based on the second optical transceiver 1-2.
[0150] Then, one optical transceiver 1 performs the synthesis of the absorption line cumulative distribution (step ST204). For example, the first optical transceiver 1-1 performs the synthesis of the absorption line cumulative distribution. At this time, the first optical transceiver 1-1 synthesizes the absorption line cumulative distribution calculated by itself with the absorption line cumulative distribution calculated by the second optical transceiver 1-2.
[0151] Here, for example, Figure 11 As shown, the coordinates of one end of the optical fiber 2, which serves as the side of the first optical transceiver 1-1, are set to x = 0, and the coordinates of the other end of the optical fiber 2, which serves as the side of the second optical transceiver 1-2, are set to x = L2. Furthermore, the position in the middle is set to x = L1.
[0152] In this case, firstly, the first optical transceiver 1-1 calculates as follows: Figure 13 The loss curve data shown on the left is calculated by the second optical transceiver 1-2 as follows. Figure 13 The loss curve data is shown on the right.
[0153] In addition, Figure 13 In the diagram, labels 131-1 and 131-2 represent the loss data (Lo(x)) before fiber 2 is set, and labels 132-1 and 132-2 represent the loss curve data (L(x)). Figure 13 In the examples, the areas marked 133-1 and 133-2 are the areas where the optical power is significantly reduced, and are the areas that are irradiated in large quantities.
[0154] Then, the first optical transceiver 1-1 calculates as follows: Figure 14 The differential data of the loss curve and the cumulative distribution of the absorption line shown on the left are calculated by the second optical transceiver 1-2 as follows. Figure 14 The right side shows the differential data of the loss curve and the cumulative distribution of the absorption line.
[0155] In addition, Figure 14 In the diagram, labels 141-1 and 141-2 represent the loss differential data ({Lo(x)}') before fiber 2 is set, and labels 142-1 and 142-2 represent the loss curve differential data ({L(x)}'). Figure 14 In the examples, the parts indicated by labels 143-1 and 143-2 are the parts where the power is significantly reduced and are the parts that are irradiated in large quantities.
[0156] Then, as Figure 15 As shown, the first optical transceiver 1-1 connects the cumulative absorption line distribution at the coordinates obtained from the results of both optical transceivers 1-1 and 1-2, thereby synthesizing the data. Figure 14In the example, both the first optical transceiver 1-1 and the second optical transceiver 1-2 measured the cumulative absorption line distribution at x = L1. Therefore, in this case, the first optical transceiver 1-1 can connect their respective cumulative absorption line distributions at x = L1, thereby integrating the data.
[0157] In addition, Figure 15 In the diagram, label 151 represents the loss differential data ({Lo(x)}') before fiber 2 is set (after synthesis), and label 152 represents the loss curve differential data ({L(x)}') (after synthesis).
[0158] Furthermore, the above description illustrates an operational example where the first optical transceiver 1-1 and the second optical transceiver 1-2 function as fiber optic radiation distribution meters. However, the present invention is not limited thereto; when the first optical transceiver 1-1 and the second optical transceiver 1-2 are measuring optical loss, they can also be used to synthesize optical loss.
[0159] Additionally, the above shows the... Figure 9 The optical transceiver 1 of Embodiment 3 shown has a communication function unit 114 added. However, it is not limited to this; the optical transceiver 1 of Embodiment 2 or... Figure 10 The optical transceiver 1 of Embodiment 3 shown is equipped with a communication function unit 114 and a selector 112, and can achieve the same effect as described above.
[0160] Furthermore, when a communication function unit 114 and a selector 112 are added to the optical transceiver 1 of Embodiment 2, that is, when a communication function unit 114 and a selector 112 are added to a structure that uses leakage light to fix the gain of LA1043, while one optical transceiver 1 is performing measurements, the other optical transceiver 1 is in a state where the output of the transmitted light is 0 or the transmitting side of the digital optical transceiver 110 is disconnected.
[0161] As described above, according to this embodiment 4, it includes: a communication function unit 114 that outputs data representing the calculation result of the differential calculation unit 109 as a communication signal, and obtains the communication signal from the optical transceiver 1 installed at the other end of the optical fiber 2 from the received signal obtained by the analog-to-digital converter 105; and a selector 112 that outputs a signal representing a pseudo-random code generated by the pseudo-random code generator 101 or the communication signal output by the communication function unit 114. The digital optical transmitter 102 generates and outputs transmitted light based on the signal output by the selector 112, and the differential calculation unit 109 combines the calculation result and the communication signal obtained by the communication function unit 114. Therefore, the optical transceiver system of embodiment 4, in addition to the effects of the optical transceiver 1 in embodiments 2 and 3, can also improve the dynamic range of the measurement distance.
[0162] Finally, referring to FIG16, examples of the hardware structure of the optical transceiver 1 in embodiments 1 to 4 will be described. Hereinafter, the hardware structure example of the optical transceiver 1 in embodiment 1 will be described, but the hardware structure examples of the optical transceiver 1 in embodiments 2 to 4 are also the same.
[0163] The functions of the pseudo-random code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and differential calculation unit 109 in the optical transceiver 1 are implemented by the processing circuit 51. The processing circuit 51 can be as follows: Figure 16A The hardware shown is dedicated, but it can also be like... Figure 16B The CPU (Central Processing Unit, Central Processing Device, Processing Device, Arithmetic Device, Microprocessor, Microcomputer, Processor or DSP (Digital Signal Processor)) 52 shown is executing the program stored in memory 53.
[0164] When the processing circuit 51 is dedicated hardware, it may be equivalent to a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The functions of each part of the pseudo-random code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and difference calculation unit 109 can be implemented separately by the processing circuit 51, or the functions of each part can be combined and implemented by the processing circuit 51.
[0165] When the processing circuit 51 is a CPU 52, the functions of the pseudo-random code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and differential calculation unit 109 are implemented through software, firmware, or a combination of software and firmware. The software and firmware are described as programs and stored in memory 53. The processing circuit 51 implements the functions of each unit by reading and executing the programs stored in memory 53. That is, the optical transceiver 1 has a memory for storing data executed by the processing circuit 51, such as... Figure 2The procedures shown are for each step. Alternatively, these procedures can also be described as programs that enable a computer to execute the steps and methods of the pseudo-random code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and difference calculation unit 109. Here, the memory 53 may be, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Electrically EPROM), disk, floppy disk, optical disk, compact disk, mini-disk, or DVD (Digital Versatile Disc).
[0166] Furthermore, the functions of the pseudo-random code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and differential calculation unit 109 can be partially implemented using dedicated hardware and partially implemented using software or firmware. For example, the pseudo-random code generator 101 can be implemented using a processing circuit 51 as dedicated hardware, and the ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and differential calculation unit 109 can be implemented by the processing circuit 51 reading and executing the program stored in the memory 53.
[0167] Thus, the processing circuit 51 can implement the above-mentioned functions through hardware, software, firmware, or a combination thereof.
[0168] Furthermore, it is possible to freely combine the various embodiments, modify any constituent elements of each embodiment, or omit any constituent elements in each embodiment.
[0169] Industrial availability
[0170] Compared to the conventional optical transceiver 1, the optical transceiver 1 disclosed herein is capable of measuring optical loss with high distance resolution and is suitable for optical transceivers 1 and the like capable of measuring optical loss.
[0171] Label Explanation
[0172] 1 Optical transceiver, 1-1 First optical transceiver, 1-2 Second optical transceiver, 2 Optical fiber, 51 Processing circuit, 52 CPU, 53 Memory, 101 Pseudo-random code generator, 102 Digital optical transmitter, 103 Optical circulator (transceiver switcher), 104 Analog optical receiver, 105 ADC (analog-to-digital converter), 106 Correlation processing unit, 107 Differential processing unit, 108 Differential data acquisition unit, 109 Differential calculation unit, 110 Digital optical transceiver, 111 Virtual code generator, 112 Selector, 113 Optical power adjustment unit, 114 Communication function unit, 1041 PD, 1042 TIA, 1043 LA.
Claims
1. An optical transceiver, wherein, have: A pseudo-random code generator whose output represents a pseudo-random code signal; A digital optical transmitter that generates and transmits optical light based on a signal representing a pseudo-random code output by the pseudo-random code generator, and is capable of transmitting more than 1 Gbit. An analog optical receiver receives input light as received light and converts the received light into a received signal. A transceiver switcher outputs the transmitted light from the digital optical transmitter to one end of an optical fiber and outputs the light from the optical fiber to the analog optical receiver. An analog-to-digital converter that converts a received signal from an analog signal into a digital signal based on a received signal obtained from the analog optical receiver; The correlation processing unit performs correlation processing on the signal representing the pseudo-random code output by the pseudo-random code generator and the received signal obtained by the analog-to-digital converter, thereby calculating loss curve data. The differential processing unit performs differential processing on the loss curve data calculated by the related processing unit, thereby calculating the differential data of the loss curve. as well as The differential calculation unit calculates the difference between the loss differential data and the loss curve differential data based on the loss differential data before the optical fiber is installed and the loss curve differential data calculated by the differential processing unit.
2. The optical transceiver according to claim 1, characterized in that, The digital optical transmitter is a digital optical transmitter that performs OOK modulation.
3. The optical transceiver according to claim 1 or 2, characterized in that, The digital optical transmitter and the analog optical receiver are composed of digital optical transceivers.
4. The optical transceiver according to claim 3, characterized in that, The receiving side of the digital optical transceiver has a limiting amplifier. The transceiver switch outputs leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver to the receiving side of the digital optical transceiver, wherein the leakage light can fix the gain of the limiting amplifier.
5. The optical transceiver according to claim 4, characterized in that, The leakage light is above -20dB.
6. The optical transceiver according to claim 3, characterized in that, The receiving side of the digital optical transceiver has a limiting amplifier. The transceiver switch outputs transmit light from an optical transceiver located at the other end of the optical fiber to the receiving side of the digital optical transceiver, wherein the transmit light is based on a virtual code unrelated to the pseudo-random code used locally.
7. The optical transceiver according to claim 6, characterized in that, The optical transceiver includes: A virtual code generator that outputs a signal representing a virtual code, which is unrelated to the pseudo-random code used in an optical transceiver located at the other end of the optical fiber; and The selector outputs either a signal representing a pseudo-random code from the pseudo-random code generator or a signal representing a virtual code from the virtual code generator. The transmitting side of the digital optical transceiver generates and outputs transmit light based on the signal output by the selector.
8. The optical transceiver according to claim 6, characterized in that, The pseudo-random code generator outputs a signal representing a pseudo-random code or a signal representing a virtual code, which is unrelated to the pseudo-random code used in the optical transceiver located at the other end of the optical fiber. The transmitting side of the digital optical transceiver generates and outputs transmit light based on the signal output by the pseudo-random code generator.
9. The optical transceiver according to any one of claims 1 to 8, characterized in that, The differential calculation unit calculates the cumulative distribution of absorption lines based on the calculated differential.
10. The optical transceiver according to any one of claims 1 to 9, characterized in that, The optical transceiver includes: The communication function unit outputs data representing the calculation result of the differential calculation unit as a communication signal, and obtains the communication signal from the optical transceiver installed at the other end of the optical fiber from the received signal obtained by the analog-to-digital converter. as well as The selector outputs a signal representing a pseudo-random code generated by the pseudo-random code generator, or a communication signal output by the communication function unit. The digital optical transmitter generates and outputs transmitted light based on the signal output by the selector. The differential calculation unit integrates the calculation results based on the calculation results and the communication signals obtained by the communication function unit.