Optical signal processing device and optical signal transmission system

Abstract

Provided is an optical signal processing device with which it is possible to reduce the influence of wavelength dispersion in wavelength division multiplexing communication. An optical signal processing device according to the present disclosure comprises: an input waveguide (301a) to which a wavelength multiplexed signal is inputted; an optical branching waveguide (302) configured to branch the wavelength multiplexed signal from the input waveguide into a plurality of arm waveguides; a plurality of wavelength-selective waveguides (303a, 303b) respectively connected to the plurality of arm waveguides and each configured to select an optical signal from the branched wavelength multiplexed signal; and an optical joining waveguide (302, 304) configured to join light beams from the plurality of arm waveguides.

Description

Technical Field

[0001] The present invention relates to an optical signal processing device and an optical signal transmission system used in an optical communication network.

Background Art

[0002] Due to the explosive spread of data communication networks such as the Internet, the demand for increasing the capacity of optical communication networks is continuously expanding. To meet such requirements for optical communication networks, wavelength division multiplexing (WDM) communication has been put into practical use. In particular, in Ethernet (registered trademark), which is a short-distance communication standard, optical technology has been applied for extension, and WDM of about four wavelengths has been applied. Therefore, a transceiver in optical Ethernet includes a wavelength multiplexer / demultiplexer that multiplexes and demultiplexes WDM signals of about four wavelengths. For miniaturization of the transceiver, a wavelength multiplexer / demultiplexer in which a plurality of dielectric multilayer films having different wavelength transmission characteristics are mounted, or a transceiver using an arrayed waveguide grating formed on an optical waveguide substrate has been put into practical use.

[0003] FIG. 1 is a diagram showing a configuration example of a general small transceiver. The transceiver 10 shown in FIG. 1 is for a transceiver on the receiving side. The transceiver 10 includes an optical waveguide substrate 11 on which a single-mode input waveguide 13, an arrayed waveguide grating 12, and a multi-mode 4-channel output waveguide 14 are formed, a 4-channel PD (PhotoDetector) array 18, a lens 15 that couples an optical signal to the input waveguide 13, and a microlens array (graded-index (GRIN) lens) 16 that couples the optical signal from the 4-channel output waveguide 14 to the 4-channel PD array 18. The 4-channel PD array 18 is mounted on a ceramic carrier 17 on which wiring 19 is formed. The distance between the 4-channel PD array 18 and the microlens array 16 is maintained by a spacer 20. As shown in FIG. 1, the optical signal input to the arrayed waveguide grating 12 is split into four optical signals by the arrayed waveguides and input to the 4-channel PD array 18.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

[0005] On the other hand, in optical Ethernet, the communication wavelength has been set to the 1.3 μm band, which is the zero-dispersion wavelength of single-mode optical fiber, to avoid waveform distortion caused by chromatic dispersion in optical fiber. However, as the signal baud rate increases with increasing capacity, optical signal distortion is becoming non-negligible even at 1.3 μm.

[0006] Figure 2 shows the wavelength and chromatic dispersion in a typical single-mode optical fiber. The relationship between wavelength λ and chromatic dispersion coefficient D is expressed by Equation 1 and Equation 2. λ 0min is the minimum zero-dispersion wavelength, and λ 0max is the maximum zero dispersion wavelength, and S 0min is the minimum zero-dispersion slope, and S 0max is the maximum zero dispersion slope.

[0007]

number

[0008]

number

[0009] In Figure 2, the four vertical lines represent the grid wavelengths standardized in the WDM standard for optical Ethernet (LAN-WDM: 800 GHz intervals (approximately 4 nm intervals)). As shown in Figure 2, as the wavelength becomes shorter from the zero-dispersion wavelength of 1.31 μm, the absolute value of chromatic dispersion increases, and waveform distortion becomes impossible to ignore. It is desirable to reduce the effects of chromatic dispersion in wavelength division multiplexing communications in Ethernet.

[0010] The present disclosure has been made in view of such problems, and its purpose is to reduce the influence of chromatic dispersion in wavelength division multiplexing communications.

[0011] An optical signal processing apparatus according to an embodiment of the present invention includes an input waveguide that inputs a wavelength-division multiplexed signal, an optical branching waveguide configured to branch the wavelength-division multiplexed signal from the input waveguide into a plurality of arm waveguides, a plurality of wavelength-selective waveguides connected to each of the plurality of arm waveguides and configured to select an optical signal from among the wavelength-division multiplexed signals that are branched, and an optical combining waveguide configured to combine the light from the plurality of arm waveguides.

[0012] According to this configuration, it is possible to reduce the influence of wavelength dispersion in wavelength-division multiplexing communication.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the optical signal processing device of the present disclosure will be described with reference to the drawings. The same or similar reference numerals indicate the same or similar elements, and repeated descriptions may be omitted. The numerical values in the following description are examples, and the optical signal processing device of the present disclosure can be implemented with other numerical values without departing from the gist.

[0015] Hereinafter, an embodiment of the present disclosure will be described on the assumption that the receiver transceiver separates and receives four optical signals with wavelengths λ0, λ1, λ2, and λ3 from a wavelength division multiplexing (WDM) signal transmitted by the transmitter transceiver via an optical fiber.

[0016] (Embodiment 1) Referring to FIG. 3A, an optical signal processing device according to an embodiment of the present disclosure will be described. FIG. 3A is a diagram showing the schematic configuration of an optical signal processing device according to an embodiment of the present disclosure. In the present embodiment, an optical signal processing device that operates as a wavelength demultiplexer (demultiplexing filter) in a receiver transceiver will be described, but it is also possible to operate as a wavelength multiplexer (multiplexing filter) of a transmitter transceiver by propagating an optical signal in the opposite direction to the following description.

[0017] The optical signal processing device shown in FIG. 3A shows a configuration in which four optical signal processing devices 300a, 300b, 300c, and 300d are connected in series, but it can also be configured with a single optical signal processing device instead of a series connection configuration.

[0018] The optical signal processing device 300a includes an input waveguide 301a, a first optical branching / combining waveguide 302 that branches light into a plurality of arm waveguides, a plurality of wavelength selective waveguides 303a and 303b connected to each of the plurality of arm waveguides, and a second optical branching / combining waveguide 304 configured to combine light. Further, the optical signal processing device 300a includes an output waveguide 301b connected to the first optical branching / combining waveguide 302, and output waveguides 305a and 305b connected to the second optical branching / combining waveguide 304. The configuration of the wavelength selective waveguide 303 will be described later.

[0019] The optical signal processing device 300a includes an input waveguide 301a for inputting a wavelength division multiplexed (WDM) signal.

[0020] The first optical branching / combining waveguide 302 is configured to branch the WDM signal from the input waveguide 301a into a plurality of arm waveguides. Further, the first optical branching / combining waveguide 302 is configured to combine the light from the plurality of arm waveguides and couple it to the output waveguide 301b. In this embodiment, two cases of the arm waveguides will be described, but the number of arm waveguides can be three or more. The number Two cases of the arm waveguides will be described, but the number of arm waveguides can be three or more.

[0021] Each of the two wavelength selective waveguides 303a and 303b is configured to select an optical signal from among the branched WDM signals. The wavelength selective waveguides 303a and 303b selectively reflect a specific single wavelength λ0 among the WDM wavelengths and transmit the rest of the WDM signals (wavelengths λ1, λ2, and λ3). The details of the configuration of the wavelength selective waveguides 303a and 303b will be described later.

[0022] The second optical branching / combining waveguide 304 is configured to combine the light from the wavelength selective waveguides 303a and 303b and couple it to the output waveguides 305a and 305b. Further, the second optical branching / combining waveguide 304 is configured to branch the light from the output waveguides 305a and 305b and couple it to the wavelength selective waveguides 303a and 303b.

[0023] The first optical branching / combining waveguide 302 and the second optical branching / combining waveguide 304 can be, for example, a 2×2 directional coupler, a 2×2 multimode interference (MMI) coupler, or a 2×2 cross waveguide formed on an optical waveguide substrate having two input ports and two output ports with a branching ratio of 50%. The two arm waveguides connecting the first optical branching / combining waveguide 302 and the second optical branching / combining waveguide 304 have equal lengths. Thus, according to the general characteristics of a Mach-Zehnder interferometer type waveguide circuit, the phase states of the optical signals of two wavelengths λ0 reflected by the wavelength selective waveguides 303a and 303b are in a state of being coupled to the output waveguide 301b in the first optical branching / combining waveguide 302. Also, the phase states of the optical signals of two wavelengths λ1, λ2, and λ3 transmitted through the wavelength selective waveguides 303a and 303b are in a state of being coupled to the output waveguide 305a in the second optical branching / combining waveguide 304. However, depending on the wavelength dependence and manufacturing errors of the optical branching / combining waveguide, light from the two arm waveguides may combine and be coupled to the input waveguide 301a. Therefore, in order to prevent propagation toward the transmitter on the transmission side, an isolator (not shown) may be arranged in the input waveguide 301a. Note that the number of input ports and output ports is not limited to two and may be three or more. For example, the first optical branching / combining waveguide 302 is configured using a 3×3 directional coupler, and a WDM signal input from one of the three input ports is branched into three arm waveguides connected to three output ports, and the optical signals of three wavelengths λ0 reflected by the three wavelength selective waveguides can be coupled to one or two of the remaining input ports of the three input ports.

[0024] In Fig. 3A, the WDM signal input from the input waveguide 301a described as WDM in / WDM out is branched into two by the first optical branching / combining waveguide 302 and then propagates to the wavelength selective waveguides 303a and 303b, respectively. The optical signals with wavelength λ0 reflected in the wavelength selective waveguides 303a and 303b propagate to the first optical branching / combining waveguide 302 and are combined to the output waveguide 301b described as Lane#0. Further, the optical signal with wavelength λ0 is received by a PD (not shown) disposed at the tip of the output waveguide 301b. On the other hand, the rest of the WDM signal (wavelengths λ1, λ2, and λ3) that has passed through the wavelength selective waveguides 303a and 303b propagates to the second optical branching / combining waveguide 304 and is combined to the output waveguide 305 a and combined to the output waveguide 305.

[0025] The optical signal processing device shown in Fig. 3A has a configuration in which a plurality of unit blocks are connected in series with the above-described optical signal processing device 300a as a unit block. That is, in the optical signal processing device shown in Fig. 3A, the output waveguide 305a of the first unit block 300a is connected to the input waveguide 301a of the second unit block 300b, the output waveguide 305a of the second unit block 300b is connected to the input waveguide 301a of the third unit block 300c, and the output waveguide 305a of the third unit block 300c is connected to the input waveguide 301a of the fourth unit block 300d. Here, the wavelength selective waveguides 303a and 303b, 303c and 303d, 303d and 303e, and 303f and 303g in the unit blocks 300a to 300d are configured such that the selected wavelengths are different.

[0026] Specifically, the wavelength selective waveguides 303c and 303d are configured to selectively reflect a specific single wavelength λ1, the wavelength selective waveguides 303e and 303f are configured to selectively reflect a specific single wavelength λ2, and the wavelength selective waveguides 303g and 303h are configured to selectively reflect a specific single wavelength λ3 among the WDM wavelengths.

[0027] As a result, the optical signal processing device shown in FIG. 3A functions as a multiplexing filter that selectively separates optical signals of different wavelengths included in the WDM wavelengths input from the input waveguide 301a of the first input block into Lane#0, 1, 2, and 3, respectively.

[0028] As described above, when operating the optical signal processing device of FIG. 3A as a multiplexing filter of a transmitter transceiver, optical signals with wavelengths λ0, λ1, λ2, and λ3 may be input from Lane#0, 1, 2, and 3 and output from the input waveguide 301a described as WDM in / WDM out. In this case, due to manufacturing errors in the wavelength-selective waveguides 303a and 303b, the optical signals of the input wavelengths are not completely reflected and are coupled to the output waveguide 305 described as Monitore#0, 1, 2, and 3, and the output waveguide 305 can be used as a monitor port. Although a configuration in which four unit blocks corresponding to four Lanes are connected in series has been described, the number of Lanes and unit blocks may be four or more.

[0029] (Modified form) As described above, in the unit block 300 having the configuration of the Mach-Zehnder interferometer type waveguide circuit, the optical signal input from the input waveguide 301a propagates through the arm waveguides and then merges and propagates to the output waveguide 305a on the cross-port side with respect to the input waveguide 301a.

[0030] Generally, a Mach-Zehnder interferometer type waveguide circuit is characterized in that the output waveguide 305b on the bar-port side has a small loss and the output waveguide 305a on the cross-port side has a large loss with respect to the input waveguide 301a. It is known that when the branching ratio or coupling ratio of the branching and merging circuit constituting the Mach-Zehnder interferometer deviates from 50%, loss occurs in the output waveguide 305a on the cross-port side and the extinction ratio deteriorates in the output waveguide 305b on the bar-port side.

[0031] Therefore, in the configuration of the optical signal processing apparatus of FIG. 3A, among the WDM signals input from the input waveguide 301a of the optical signal processing apparatus 300a, the optical signal with wavelength λ3 passes through the cross port three times before being output from the output waveguide 301b described in Lane #3, resulting in an increase in loss.

[0032] Referring to FIG. 3B, a modified form of the optical signal processing apparatus according to an embodiment of the present disclosure will be described. The optical signal processing apparatus shown in FIG. 3B has a configuration that solves the problem of increased loss.

[0033] The optical signal processing apparatus shown in FIG. 3B is different from the optical signal processing apparatus shown in FIG. 3A in that, in each of the unit blocks 300a to 300d, one of the two arm waveguides connecting the first optical branching / combining waveguide 302 and the second optical branching / combining waveguide 304 is provided with an optical path length adjustment waveguide 306 for adjusting the optical path length of the propagating light between the wavelength selective waveguide 303a or 303b and the second optical branching / combining waveguide 304. Further, the optical signal processing apparatus shown in FIG. 3B is different from the optical signal processing apparatus shown in FIG. 3A in that the output waveguide 305b of the second unit block 300b is connected to the output waveguide 301b of the third unit block 300c. Furthermore, the optical signal processing apparatus shown in FIG. 3B is different from the optical signal processing apparatus shown in FIG. 3A in that a WDM signal is input from the output waveguide 301b of the first unit block 300a, an optical signal with wavelength λ0 is output from the input waveguide 301a (Lane #0) of the first unit block 300a, an optical signal with wavelength λ2 is output from the input waveguide 301a (Lane #2) of the third unit block 300c, and the output waveguides 305a of the second unit block 300b and the fourth unit block 300d can be used as the monitor ports of Lane #2 and #3, respectively.

[0034] In FIG. 3B, since the arm lengths between the first optical branching / combining waveguide 302 and the wavelength selective waveguides 303a and 303b are set to be the same, the reflected optical signal of λ0 is output to Lane#0. On the other hand, two optical path length adjustment waveguides 306 are installed in one of the two arm waveguides so that the remaining WDM signals (λ1, λ2, and λ3) that have passed through the wavelength selective waveguides 303a and 303b are output to the bar port (output waveguide 305a) of the Mach-Zehnder interferometer. Similarly, optical path length adjustment waveguides are installed in the second, third, and fourth unit blocks 300b, 300c, and 300d as well. As a result, the optical signals of each signal λ1 to λ4 are output only once to the cross port of the unit block until they are output to Lane#0 to #3 on the left side of FIG. 3B. That is, according to the configuration of FIG. 3B, it is possible to configure an optical signal processing device with small loss.

[0035] (Embodiment 2) Referring to FIG. 4, an optical signal processing device according to an embodiment of the present disclosure will be described. FIG. 4 is a diagram showing a schematic configuration of the wavelength selective waveguide 303 in the optical signal processing device 300 referred to as the unit block in FIGS. 3A and 3B. Descriptions overlapping with the above descriptions are omitted.

[0036] In FIG. 4, the wavelength selective waveguide 303 is a waveguide whose width changes in a plurality of cycles in the optical propagation direction and constitutes a Bragg grating. As shown in FIG. 4, the wavelength selective waveguide 303 has (K - 1) regions sg (K is an integer of 1 or more). In each region sgi (i = 0 to K - 1), a waveguide whose width alternates between Wn and Ww with a period of Λi (i = 1 to K - 1) constitutes a Bragg grating. The period Λi in the region sgi gradually changes and gradually becomes longer along the optical propagation direction. That is, as a whole, it has a configuration of a chirped Bragg grating (CGB).

[0037] The WDM signal (wavelengths λ0, λ1, ···, and λ ( K -1) ) input from the left side in FIG. 4 is in the region sg0, n effis the transmission refractive index of the Bragg grating, and its Bragg wavelength λ0=2n eff ×Λ0, and other wavelengths are transmitted. Then, the remaining WDM signals (wavelengths λ1, λ2, . . . and λ(K-1)) that have passed through the region sg0 are reflected in the region sg2, where λ1=2n eff ×Λ1) is reflected, and the other wavelengths are transmitted. Similarly, the remaining WDM signal (wavelength λ(K-1)) that has passed through the region sg(K-2) is reflected in the region sg(K-1) by λ (K-1) =2n eff ×Λ (K-1) Only the optical signal with the wavelength represented by is reflected, and all other wavelengths are transmitted. By connecting Bragg gratings with different periods in this way and continuously changing the grating period Λi, it is possible to selectively reflect optical signals with specific wavelengths from among the WDM wavelength signals into a rectangular shape.

[0038] Furthermore, the position in the propagation direction of light at which the optical signal is reflected in each region sg (i=0 to K-1) is determined by the wavelength λ i Therefore, a time delay occurs between the optical signals reflected at different positions. That is, since the phase of the reflected optical signal changes depending on the wavelength, the wavelength-selective waveguide 303 can impart a group delay to the reflected optical signal. The amount of group delay can be changed by changing the distance from the region sg0 to the region sg(K-1).

[0039] The change from the periods Λ0 to Λ(K-0) does not need to be linear, and any distribution can be imparted, so that a group delay with any spectral shape can be imparted.

[0040] Since the Bragg grating formed by an optical fiber is manufactured using irradiation and interference of UV light, it is difficult to change the longitudinal period. In contrast, the wavelength-selective waveguide 303 of the present disclosure has the advantage of high freedom in setting the group delay spectrum because its period Λ is set by photolithography. Here, although it has been described that each region sg0 to sg(K-1) includes a plurality of periodic structures, even a single periodic structure may be used. Also, the width Wn of the narrow portion and the width Ww of the wide portion of the wavelength-selective waveguide 303 may be set to gradually change.

[0041] (Embodiment 3) With reference to FIGS. 5 and 6, a schematic configuration of the wavelength-selective waveguide 303 in the optical signal processing apparatus 300 according to an embodiment of the present disclosure will be described. FIG. 5 is a diagram for explaining a method of determining the waveguide width. FIG. 6 is a graph showing the width distribution of the entire Bragg grating.

[0042] Generally, a Bragg grating has spectral characteristics of the Fourier transform of the spatial distribution of the grating. Therefore, there is a problem that side lobes are generated in the demultiplexing spectrum in a Bragg grating in which the widths Wn and Ww of the wavelength-selective waveguide 303 shown in FIG. 4 are simply interchanged with each other.

[0043] Apodization is effective for solving this problem. In an optical fiber Bragg grating, apodization is automatically performed by the distribution of the irradiated UV light, whereas in a Bragg grating formed by a waveguide, it is necessary to perform apodization by controlling the width of the waveguide.

[0044] Furthermore, the transmission refractive index n eff of the Bragg grating needs to be constant in the longitudinal direction.

[0045] FIG. 5 is a diagram showing the relationship between the waveguide width w and the transmission refractive index n eff in a silica-based optical waveguide. The transmission refractive index n eff can be expressed by the approximate formula of Equation 2. n Max , n Minand w0 are constants obtained experimentally or by numerical calculation.

[0046]

Number

[0047] In FIG. 5, the relative refractive index difference of the waveguide is 2%. First, the central average transmission refractive index nc is set. Next, the amount of refractive index variation δn induced by modulating the waveguide width is set, and the maximum refractive index nh = nc + δn and the minimum refractive index nl = nc - δn are determined. δn affects the bandwidth and reflectivity of the Bragg wavelength, and the larger it is, the better. Finally, from FIG. 5, the waveguide widths Wn and Ww that give the maximum refractive index nh and the minimum refractive index nl are determined.

[0048] To set the apodization, δn is gradually increased in the first and last regions of the entire region constituting the Bragg grating above. That is, in the first region, the refractive index change is made larger from the end to the central region, and in the last region, the refractive index change is made smaller from the central region to the end (setting the apodization), thereby suppressing the side lobes. FIG. 6 is a graph showing the width distribution in the entire Bragg grating.

[0049] (Embodiment 4) Referring to FIG. 7, an optical transmission system according to an embodiment of the present disclosure will be described. The optical transmission system of this embodiment is a system in which a transmitter (Tx) on the transmission side including the above-described optical signal processing device as a wavelength multiplexer and a receiver (Rx) on the reception side including the optical signal processing device as a wavelength demultiplexer are connected by an optical fiber. Hereinafter, a design example of the Bragg grating in each optical signal processing device will be described.

[0050] In the chirped Bragg grating (CBG) described above, when the set value of wavelength dispersion is zero, the length of the entire Bragg grating cannot be set to a sufficient length, so sufficient reflectivity cannot be obtained. This significantly affects, for example, the case of Lane#0 where a grid is set at the zero-dispersion wavelength. Similarly, if all dispersion is compensated by either the multiplexing filter on the transmission side or the demultiplexing filter on the reception side, the dispersion value to be imparted by the other of the demultiplexing filter on the reception side or the multiplexing filter on the transmission side needs to be zero. Similarly, the entire length of the Bragg grating with a sufficient length cannot be ensured, and sufficient filter reflectivity cannot be obtained.

[0051] Therefore, in the present disclosure, the above problem is solved by imparting a specific amount of dispersion in addition to the required amount of dispersion for compensating the wavelength dispersion generated in the optical fiber.

[0052] FIG. 7 is a diagram for explaining the amount of dispersion imparted in the multiplexing filter on the transmission side and the demultiplexing filter on the reception side in order to compensate for the wavelength dispersion generated in the optical fiber. For the amount of dispersion generated for each lane of the WDM signal in the optical fiber, that is, the required amount of dispersion Df [ps / nm] to be compensated (Df < 0 in FIG. 7), the amount of dispersion DTx [ps / nm] given on the transmission side (DTx > 0 in FIG. 7) and the amount of dispersion DRx [pnm] given on the reception side (DRx < 0 in FIG. 7) are set so as to satisfy DTx + Df + DRx = 0.

[0053] As a result, in both the optical signal processing device that the transceiver on the signal side has as a wavelength multiplexer and the optical signal processing device that the transceiver on the reception side including has as a wavelength demultiplexer, the entire length of the Bragg grating with a sufficient length can be ensured, and sufficient filter reflectivity can be obtained.

[0054] Figures 8(a) and 8(b) show the transmission spectrum and reflection spectrum of the Bragg grating of the optical signal processing device using a quartz-based optical waveguide in the transmitter and receiver transceivers according to this embodiment, respectively. In the graphs shown in Figures 8(a) and 8(b), the group delay (dashed-dotted line) is shown together with the spectrum of the optical signal intensity of the reflected light (solid line) and the optical intensity spectrum of the transmitted light (dashed line).

[0055] In Figures 8(a) and 8(b), it is filtering of the LAN-WDM wavelengths (800 GHz interval) assuming four-wavelength wavelength multiplexing used in Ethernet, and it is a graph considering the method of imparting the dispersion described above with reference to Figure 7.

[0056] Note that the parameters of the Bragg grating were used with the values shown in Table 1 below assuming 10 km transmission in consideration of Figure 2.

[0057]

Table 1

[0058] As shown in Figures 8(a) and 8(b), it can be seen that good transmission characteristics and dispersion characteristics are obtained for each lane.

[0059] (Embodiment 5) With reference to Figure 9, an optical signal processing device according to an embodiment of the present disclosure will be described. Figures 9(a) and 9(b) are diagrams showing the schematic configuration of the optical signal processing device according to an embodiment of the present disclosure. The optical signal processing devices in Figures 9(a) and 9(b) have a layout of the first unit block 300a, the second unit block 300b, the third unit block 300c, and the fourth unit block 300d connected in series, which is different from the optical signal processing devices in Figures 3A and 3B.

[0060] In Figure 9(a) indicatesThe optical signal processing device is configured to arrange a first unit block 300a, a second unit block 300b, a third unit block 300c, and a fourth unit block 300d such that the propagation direction of light in adjacent unit blocks changes by 180 degrees. In this way, by arranging the unit blocks in a folded manner (changing the direction by 180 degrees), the chip footprint of the entire optical signal processing device can be reduced.

[0061] The optical signal processing device shown in FIG. 9(b) is configured to arrange a first unit block 300a, a second unit block 300b, a third unit block 300c, and a fourth unit block 300d such that the propagation direction of light is inverted by more than 180 degrees. By arranging the unit blocks in this way, with the direction changed by more than 180 degrees and folded, further miniaturization of the chip of the entire optical signal processing device is possible.

[0062] That is, when arranging with a 180-degree fold as shown in FIG. 9(a), with the minimum bending radius of the waveguide being R, the vertical size of FIG. 9(a) is 6R + S. Here, S is the separation width between the two arms of the Mach-Zehnder interferometer. On the other hand, the vertical size of FIG. 9(b) is about 4R + 2S. Generally, S can be made small enough so that adjacent waveguides do not couple, while R needs to be made large enough so that no loss occurs. For example, in the case of a silica-based optical waveguide having a relative refractive index difference of 1.5%, R is about 2 mm. On the other hand, since S is set to about the outer shape of the optical fiber, S = 0.125 μm. Therefore, the vertical size is 12.125 mm in the case of the configuration of FIG. 9(a), while it is 8.25 mm in the case of the configuration of FIG. 9(b), enabling miniaturization compared to FIG. 9(a).

Industrial Applicability

[0063] According to the optical signal processing device of the present disclosure, it is possible to reduce the influence of wavelength dispersion in wavelength division multiplexing communication.

Explanation of Signs

[0064] 300 Optical signal processing device 301a Input waveguide 301b Output waveguide 302 Optical branching / combining waveguide 303a, 303b, 303c, 303d, 303e, 303f, 303g, 303h Wavelength selective waveguide 304 Optical branching / combining waveguide 305a, 305b Output waveguide 306 Optical path length adjustment waveguide

Claims

1. An input waveguide for inputting a wavelength-division multiplexed signal, An optical branching waveguide configured to branch the wavelength-division multiplexed signal from the input waveguide into a plurality of arm waveguides, A plurality of wavelength-selective waveguides connected to each of the plurality of arm waveguides, each configured to select an optical signal from among the branched wavelength-division multiplexed signals, An optical combining waveguide configured to combine the light from the plurality of arm waveguides An optical signal processing apparatus comprising: Each of the plurality of wavelength-selective waveguides is configured to reflect an optical signal selected from the branched wavelength-division multiplexed signal and transmit the rest of the branched wavelength-division multiplexed signal, The optical combining waveguide configured to combine the light from the plurality of arm waveguides, Combines the reflected optical signals from the plurality of arm waveguides, Combines the rest of the transmitted wavelength-division multiplexed signals from the plurality of arm waveguides Is configured as follows, The optical signal processing apparatus, A second input waveguide for inputting the rest of the combined wavelength-division multiplexed signal as a second wavelength-division multiplexed signal, A second optical branching waveguide configured to branch the second wavelength-division multiplexed signal from the second input waveguide into a plurality of second arm waveguides, A plurality of second wavelength-selective waveguides connected to each of the plurality of second arm waveguides, each configured to select an optical signal from among the branched second wavelength-division multiplexed signals, A second optical combining waveguide configured to combine the light from the plurality of second arm waveguides An optical signal processing apparatus further comprising:

2. The optical signal processing apparatus according to claim 1, wherein at least one of the plurality of arm waveguides includes an optical path length adjustment waveguide.

3. Each of the plurality of second wavelength-selective waveguides is configured to reflect an optical signal selected from the branched second wavelength-division multiplexed signal and transmit the rest of the branched second wavelength-division multiplexed signal, The second optical combining waveguide configured to combine the light from the plurality of second arm waveguides, Combines the reflected optical signals from the plurality of second arm waveguides, Combines the rest of the transmitted wavelength-division multiplexed signals from the plurality of second arm waveguides Is configured as follows, The optical signal processing apparatus, A third input waveguide that inputs the light combined by the second optical multiplexing waveguide as a third wavelength multiplexed signal, A third optical branching waveguide configured to branch the third wavelength multiplexed signal from the third input waveguide into a plurality of third arm waveguides, A plurality of third wavelength selective waveguides connected to each of the plurality of third arm waveguides, each configured to select an optical signal from among the branched third wavelength multiplexed signals, A third optical multiplexing waveguide configured to multiplex the light from the plurality of third arm waveguides, The optical signal processing apparatus according to claim 1, further comprising.

4. The wavelength selective waveguide has one or more regions in the light propagation direction, The wavelength selective waveguide is a waveguide whose width changes periodically, The periods of change of the width in the one or more regions are different, In each of the one or more regions, the amount of change in the width at the start end and the end is smaller than the amount of change in the width other than the start end and the end. The optical signal processing apparatus according to claim 1.

5. An input waveguide for inputting a wavelength multiplexed signal, An optical branching waveguide configured to branch the wavelength multiplexed signal from the input waveguide into a plurality of arm waveguides, A plurality of wavelength selective waveguides connected to each of the plurality of arm waveguides, each configured to select an optical signal from among the branched wavelength multiplexed signals, An optical multiplexing waveguide configured to multiplex the light from the plurality of arm waveguides, Comprising, The wavelength selective waveguide has one or more regions in the light propagation direction, The wavelength selective waveguide is a waveguide whose width changes periodically, The periods of change of the width in the one or more regions are different, In each of the one or more regions, the amount of change in the width at the start end and the end is smaller than the amount of change in the width other than the start end and the end. An optical signal processing apparatus.

6. An optical signal transmission system including a transmission side transponder and a reception side transponder connected by an optical fiber, The transmission side transponder and the reception side transponder each include the optical signal processing apparatus according to any one of claims 1 to 5, With respect to the dispersion amount Df imparted by the optical fiber, such that the finite dispersion amount DTx + the finite dispersion amount DRx = the dispersion amount Df is satisfied, a finite dispersion amount DTx is set in the wavelength-selective waveguide of the transmitting-side transponder, and a finite dispersion amount DRx is set in the wavelength-selective waveguide of the receiving-side transponder, an optical signal transmission system.

Images