JP2013246312A - Wavelength multiplexer/demultiplexer and optical receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain wavelength multiplexing and demultiplexing with low loss property and low crosstalk while reducing a manufacturing cost and consumption power.SOLUTION: A wavelength multiplexer/demultiplexer includes an optical multiplexing/demultiplexing circuit for multiplexing and demultiplexing light signals having different wavelengths included in input light, and an add/drop type ring resonator optically connected to each of a plurality of outputs of the optical multiplexing/demultiplexing circuit. The add/drop type ring resonator includes a ring region, a through waveguide connected to a through port, and a drop waveguide connected to a drop port. The resonance center wavelength of the add/drop type ring resonator corresponds to each multiplexing/demultiplexing wavelength of the optical multiplexing/demultiplexing circuit, and light taken out from the drop port is defined as output after wavelength separation.

Description

  The present invention relates to a wavelength multiplexer / demultiplexer and an optical receiver using the same.

  In recent years, an optical device has been formed on a silicon (Si) substrate for high-capacity interconnects, and the processing capacity per optical wiring has been improved by using wavelength division multiplexing (WDM) technology. Has been actively considered. In order to transmit / receive a WDM signal within a silicon chip, a WDM optical signal is usually multiplexed / demultiplexed as required using a wavelength multiplexer / demultiplexer. The characteristics required for the wavelength multiplexer / demultiplexer include low loss and low crosstalk (XT). Increasing the number of channels is effective in making the most of the advantages of WDM.

  As a wavelength multiplexer / demultiplexer suitable for multi-channeling, an arrayed waveguide grating (AWG) shown in FIG. 1 is known (for example, see Non-Patent Document 1). The AWG 110 includes a plurality of arrayed waveguides 113-1 to 113-k that optically connect the input star coupler 111 and the output star coupler 112. The arrayed waveguides 113-1 to 113-k (collectively referred to as “arrayed waveguide 113”) have a predetermined optical path length difference. In the case of AWG, a random phase error (phase shift) occurs in the array region where the arrayed waveguide 113 is formed, and the multiplexing / demultiplexing characteristics deteriorate. Specifically, the insertion loss of the wavelength multiplexer / demultiplexer occurs, and the crosstalk (XT) increases. This is a problem related to the accuracy of the manufacturing apparatus.

  In order to solve this problem, it is necessary to minimize the phase error (δφ) generated in the manufacturing process. However, the random phase error (δφ) is an amount that is statistically determined by the accuracy of the manufacturing apparatus. In order to fundamentally overcome the problem of the random phase error (δφ), the resolution of the manufacturing apparatus must be highly accurate. This increases the manufacturing cost.

  FIG. 2 is a diagram showing a combined / demultiplexed spectrum characteristic when a 16-channel AWG having 41 arrayed waveguides 113 is manufactured with different process accuracy. 2A is a spectral characteristic plotting the output of one channel of an AWG produced by a DUV248 nm, 180 nm node CMOS process, and FIG. 2B is the output of one channel of an AWG produced by a DUV193 nm, 65 nm node CMOS process. Is a spectral characteristic. In each process node, the crosstalk (XT) is worse than −20 dB in the case of FIG. It is difficult to improve this from -20 dB. On the other hand, as shown in FIG. 2B, it can be expected that the crosstalk is improved to −30 dB by raising the process node, but the manufacturing cost increases.

  As another method for overcoming the problem of the phase error (δφ), it has been proposed to individually adjust the phase shift generated in the array area of the AWG (see, for example, Non-Patent Document 2). However, this method requires control of all tens of arrayed waveguides, which makes the control algorithm extremely complicated. There is also a problem that power consumption increases because the arrayed waveguide region having a relatively large area is controlled.

D. -J. Kim, J. -M. Lee, J. -H. Song, J. -H. Pyo, and G. -O.Kim, “Crosstalk reduction in a shallow-etched silicon nanowire AWG,” PhotonicsTechnology Letters, Vol (20), No (19), October, 2008 NK Fontaine, J. Yang, W. Jiang, DJ Geisler, K. Okamoto, R. Huang, and SJB Yoo, “Active arrayed-waveguide grating with amplitude and phase control for arbitrary filter generation and high-order dispersioncompensation,” Proceedings of ECOC (European Conference on Optical Communication Conference), Mo.4.C.3, September, 2008

  As described above, in order to reduce AWG crosstalk, it is necessary to reduce the phase error (δφ) generated in the arrayed waveguide region. However, increasing the accuracy of the apparatus inevitably increases the manufacturing cost. In addition, the individual phase adjustment in the AWG array region complicates the control algorithm and is difficult to design, and also increases the power consumption.

  Therefore, it is an object to reduce loss and crosstalk in wavelength multiplexing / demultiplexing while suppressing manufacturing cost and power consumption.

In one aspect, the wavelength multiplexer / demultiplexer
An optical multiplexing / demultiplexing circuit for multiplexing / demultiplexing optical signals of different wavelengths included in the input light;
An add / drop ring resonator optically connected to each of the plurality of outputs of the optical multiplexing / demultiplexing circuit, wherein the add / drop ring resonator includes a ring region and a through port connected to a through port. Including a waveguide and a drop waveguide connected to the drop port;
The resonance center wavelength of each of the add / drop type ring resonators corresponds to each of the multiplexing / demultiplexing wavelengths of the optical multiplexing / demultiplexing circuit, and the light extracted from the drop port is used as an output after wavelength separation. To do.

  It is possible to realize wavelength multiplexing / demultiplexing with low loss and low crosstalk while suppressing manufacturing cost and power consumption.

1 is a schematic diagram of an arrayed waveguide grating (AWG) used as a multiplexer / demultiplexer. FIG. It is a spectral characteristic figure of the array wavelength depending on the precision of a manufacturing apparatus. It is a schematic block diagram of the wavelength multiplexer / demultiplexer of one Embodiment. FIG. 4 is a diagram illustrating a modification of the wavelength multiplexer / demultiplexer in FIG. 3. FIG. 5 is a diagram showing a configuration in which the output of the wavelength multiplexer / demultiplexer of FIG. 4 is connected to a light receiving element for reception. FIG. 5 is a diagram illustrating a configuration example of a wavelength multiplexer / demultiplexer when an interference multiplexer / demultiplexer is used instead of the arrayed waveguide grating of FIG. 3 or FIG. 4. FIG. 4 is a diagram of a spectral response obtained from a drop port and a spectral response obtained from a through port when the wavelength multiplexer / demultiplexer of FIG. 3 is manufactured by a DUV 248 nm, 180 nm node CMOS process. It is a schematic sectional drawing of the rib type | mold waveguide of the silicon | silicone thin wire | line applied to the wavelength multiplexer / demultiplexer of embodiment. It is a schematic sectional drawing of the channel type | mold waveguide of the silicon | silicone thin line applied to the wavelength multiplexer / demultiplexer of embodiment. It is a schematic block diagram of the optical receiver using the wavelength multiplexer / demultiplexer of embodiment. It is a figure which compares and shows the multiplexing / demultiplexing spectrum characteristic of 16 channel AWG of embodiment compared with the multiplexing / demultiplexing spectrum characteristic device of 216 channel AWG by a prior art. It is a figure which shows the multiplexing / demultiplexing spectrum characteristic of 16 channel AWG of embodiment, and the crosstalk reduction effect. It is a figure which shows the effect of the wavelength multiplexer / demultiplexer of embodiment compared with a prior art.

  Hereinafter, embodiments of the invention will be described with reference to the drawings. In the embodiment, by performing fine adjustment of the phase of the light of each wavelength component output from the optical multiplexing / demultiplexing circuit such as AGW, the crosstalk of the wavelength multiplexing / demultiplexing device is obtained even when the accuracy of the manufacturing apparatus is the same as the conventional one Reduce.

  FIG. 3 is a schematic configuration diagram of a wavelength multiplexer / demultiplexer 1A according to an embodiment. The wavelength multiplexer / demultiplexer 1A includes an optical multiplexing / demultiplexing circuit 10 that demultiplexes light of different wavelength components included in input light, and a plurality of add / drop type rings optically connected to the outputs of the optical multiplexing / demultiplexing circuit 10 It includes resonators (AD-MRR: add-drop microring resonators) 20-1 to 20-n (collectively referred to as “add-drop type ring resonator 20” or “AD-MRR20” as appropriate).

  The optical multiplexing / demultiplexing circuit 10 is an arrayed waveguide grating (AWG) 10 in the example of FIG. The AWG 10 is an input star coupler 11, an output star coupler 12, and a plurality of array waveguides 13-1 to 13 -k (referred to as “array waveguide 13” as appropriate) having a predetermined optical path length difference between them. Included). The AWG 10 receives, from the input waveguide 2, light that is a combination of optical signals of a plurality of channels as input light. The input light spreads in the slab region 7 of the input star coupler 11 and is coupled to k arrayed waveguides 13-1 to 13-k. The optical signal to which a predetermined phase difference is given by the arrayed waveguides 13-1 to 13-k is coupled to the slab region 8 of the output star coupler 12, and the corresponding output waveguide 3-1 with a diffraction angle corresponding to the wavelength. To 3-n (collectively referred to as “output waveguide 3” where appropriate). The number n of the output waveguides 3 may be the same as or different from the number k of the arrayed waveguides 13.

  The add / drop ring resonator 20 optically connected to each output waveguide 3 of the AWG 10 has a ring region 23, a through waveguide 21 connected to the through port, and a drop waveguide 22 connected to the drop port. The resonance center wavelengths of the AD-MRRs 20-1 to 20-n coincide with the corresponding multiplexing / demultiplexing center wavelengths of the AWG 10. Further, the circumference of the ring region 23 of the AD-MRRs 20-1 to 20-n is larger than the optical path length difference of the arrayed waveguide 13 of the AWG 10.

Specifically, when the optical path length difference of the arrayed waveguide 13 is ΔL _Array , the ring length of the ring region 23 is L _MRR , and the radius of the ring region is R, the ring loop length satisfies the following conditions.

L _MRR = 2πR> ΔL _Array (1)
L _MRR ≠ P · ΔL _Array (P is a natural number) (2)
When the condition of the expression (1) is satisfied, the bending radiation loss of the AD-MRR 20 is minimized and the loss can be reduced. In other words, the radius of curvature of the ring region 23 can be increased to such an extent that no excessive loss occurs.

  Control is performed so that the FSR (free spectral range) of the AD-MRR 20 does not coincide with an integer multiple of the FSR of the AWG 10 according to the condition of the expression (2). Thereby, the transmission peak of AWG10 in a wavelength region other than a desired operating band can be suppressed. This effect will be described later with reference to FIG.

  In each of the AD-MRRs 20-1 to 20-n, a wavelength component that matches the resonance center wavelength of the ring resonator is coupled to the ring region 23, and other components (such as a crosstalk component) are transmitted to the through port. The light coupled to the ring region 23 circulates around the ring region 23, is coupled to the drop waveguide 32, and is output to the drop port.

  By providing an add / drop type ring resonator (AD-MRR) 20, light matching the resonance center wavelength of the ring resonator is extracted (filtered) from each wavelength component, and crosstalk after multiplexing / demultiplexing is reduced. be able to. The outputs from the drop ports of the AD-MRRs 20-1 to 20-n become the output of the wavelength multiplexer / demultiplexer 1A.

  FIG. 4 is a schematic configuration diagram of a wavelength multiplexer / demultiplexer 1B which is a modification of FIG. In the configuration of FIG. 3, it is premised that the demultiplexing center wavelength of the AWG 10 matches the resonance center wavelength of the AD-MRR 20. However, there are many cases where the demultiplexing center wavelength of the AWG 10 and the resonance center wavelength of the AD-MRR 20 do not coincide with each other due to an error generated in the manufacturing process. If the amount of deviation (Δλ) between the demultiplexing center wavelength of the AWG 10 and the resonance center wavelength of the AD-MRR 20 increases, desired characteristics cannot be obtained. Therefore, the problem of wavelength shift is solved by tuning the resonance center wavelength of the AD-MRR 20.

  The wavelength multiplexer / demultiplexer 1B includes the AWG 10 and AD-MRRs 30-1 to 30-n that are optically connected to the outputs of the AWG 10. The AD-MRR 30 includes a ring region 33, a through waveguide 31, a drop waveguide 32, and a heater electrode 35 that heats the ring region 33. For example, the heater electrode 35 is formed on an upper layer of the layer in which the ring region 33, the through waveguide 31 and the drop waveguide 32 are formed via an insulating film. Each heater electrode 35 is connected to a pad electrode 37 for applying voltage or current.

  A light receiver 36 (PD1) is connected to the through waveguide 31, and the current value of the optical signal output from the output waveguide 3 of the AWG 10 is monitored. The voltage or current applied to the heater electrode 35 is adjusted according to the monitor result, and the refractive index of the ring region 23 is changed. As a result, the resonance center wavelength of the AD-MRR 30 is shifted in the direction in which the wavelength shift amount (Δλ) is reduced, and is matched with the demultiplexing center wavelength of the AWG 10.

  The area of the AD-MRR 30 is 1/100 or less of the area of the arrayed waveguide region of the AWG 10. Therefore, even when each AD-MRR 30 is individually controlled, it is possible to reduce power consumption necessary for wavelength control.

  As shown in FIG. 5, an optical receiver can be configured by connecting a receiving light receiver 40 (PD2) to the drop port of each AD-MRR 30. The optical receiver will be described later with reference to FIG.

  FIG. 6 is a schematic configuration diagram of a wavelength multiplexer / demultiplexer 1C which is another modification of FIG. 3 and 4, the AWG 10 is used as the optical multiplexing / demultiplexing circuit 10. However, any configuration that can multiplex / demultiplex received input light with a wavelength corresponding to each channel can be employed. In the example of FIG. 6, a delay interferometer (DMZI) type element 15 is used as the optical multiplexing / demultiplexing circuit 15. Combining Mach-Zehnder interferometers 17-1, 17-2 and 17-3, from four output waveguides 3-1, 3-2, 3-3 and 3-4 (collectively referred to as “output waveguide 3” where appropriate) Extract light of different wavelengths. In the Mach-Zehnder interferometers 17-1, 17-2, and 17-3, the optical path lengths of the two arms are set so that a predetermined optical path length difference is given to the entire waveguide. The optical path length difference between the arms can be set by changing the physical length of the waveguide or changing the refractive index of the waveguide by the thermo-optic phase shifter 18 to change the effective waveguide length. The output waveguide 3 of the delay interferometer type multiplexer / demultiplexer 15 is optically connected to the corresponding AD-MRR 20 (FIG. 3) or AD-MRR 30 (FIG. 4).

  Also with this configuration, the crosstalk can be reduced by the AD-MRR 20 (or 30) arranged at the subsequent stage of the optical multiplexing / demultiplexing circuit (delay interferometer type multiplexing / demultiplexing element) 15.

  FIG. 7 is a diagram showing the spectral characteristics when the wavelength multiplexer / demultiplexer 1A of FIG. 3 is fabricated by the same DUV 248 nm, 180 nm node CMOS process as FIG. The solid line in FIG. 7A is the spectral response from the drop port of the AD-MRR 20, and the solid line in FIG. 7B is the spectral response from the through port of the AD-MRR 20. As a comparative example, the spectral response from the output port of the wavelength multiplexer / demultiplexer 110 having the conventional configuration shown in FIG.

  The spectral response of the drop port (FIG. 7 (a)) and the through port (FIG. 7 (b)) are just reversed. In FIG. 7A, when the wavelength shift (Δλ) between the center wavelength of the AWG 10 and the center wavelength of the AD-MRR 20 is zero, the spectral response of the drop port shows a peak. In FIG. 7B, when the wavelength shift (Δλ) between the AWG 10 and the AD-MRR 20 is zero, the spectral response of the through port is minimized.

  As is apparent from FIG. 7, by applying a filtering action by the AD-MRR 20 to each channel of the AWG 10, the crosstalk is reduced from −20 dB (1/100) to −30 dB (1/1000) at the drop port. be able to. It can also be seen that the excess loss at the center wavelength and the combined / demultiplexed spectrum shape are hardly affected.

  The spectral response in FIG. 7A corresponds to the current signal response from the receiving light receiver (PD2) in the optical receiver configuration in FIG. 5, and the spectral response in FIG. This corresponds to a current signal response from the monitor light receiver (PD1) in the optical receiver configuration.

  In the wavelength multiplexer / demultiplexers 1A, 1B, and 1C of the embodiment, the wavelength control of the AD-MRRs 20 and 30 is extremely simple. When the characteristics shown in FIG. 7A are obtained, the spectral characteristics from the through ports of the AD-MRRs 20 and 30 are inverted in the vicinity of the multiplexing / demultiplexing wavelength grid (FIG. 7B). At this time, the amount of monitor current from the PD 1 provided in the through port of the AD-MRR 30 of FIGS. As the wavelength shift amount (Δλ) increases, the amount of current from PD1 increases. Appropriate tuning control of the AD-MRR 30 need only be performed so that the amount of current flowing through the PD 1 is minimized. In addition, since the relative wavelength relationship of the multi-channel components is determined by the AWG 10, the optimum tuning conditions are the same in any AD-MRR.

According to the wavelength multiplexer / demultiplexer of the embodiment, it is possible not only to improve the crosstalk but also to reduce the loss by reducing the size of the AWG 10 itself. In general, in the case of AWG, as the number of channels increases, an FSR _AWG (free spectral range) greater than the bandwidth (BW _DEMUX ) expressed by (number of channels) × (channel interval) is required. This is because when the FSR _AWG becomes narrower than the bandwidth (BW _DEMUX ), some channel signals are affected by crosstalk, resulting in a large penalty. In order to widen the FSR _AWG , the optical path length difference (ΔL _Array ) between the arrayed waveguides may be reduced. In this case, however, the filter bandwidth of the AWG is widened. Even if the filter bandwidth is widened, the crosstalk deteriorates. In order to reduce the filter bandwidth of the AWG, the number of arrayed waveguides must be increased.

From the above, as the number of AWG channels increases, ΔL _Array must be reduced and the number of arrayed waveguides increased. When the number of arrayed waveguides increases, the element size increases, and excess loss tends to increase when multiplexing / demultiplexing with a star coupler.

  On the other hand, in the wavelength multiplexer / demultiplexer 1 of the embodiment, the filter effect of the AD-MRR 20 (or 30) is used. The number of waveguides can be reduced. That is, the expansion of the AWG bandwidth accompanying the reduction in the number of arrayed waveguides can be compensated by narrowing the filter bandwidth of the AD-MRR 20 (or 30).

FIG. 8 is a schematic cross-sectional view of a rib-type waveguide 65 as an example of a waveguide constituting the wavelength multiplexer / demultiplexer 1 of the embodiment. The rib-type waveguide 65 can be formed using an SOI wafer having a silicon oxide (SiO ₂ ) film 62 and a Si core layer (for example, a film thickness of 0.25 μm) on the Si substrate 61. Waveguide stripes are patterned in the element region for forming the wavelength multiplexer / demultiplexer 1 by an optical exposure process. The pattern of the rib waveguide 65 is defined by a photomask of an optical exposure apparatus. Instead of light exposure, electron beam exposure may be used.

The pattern drawn on the Si core layer is dry-etched by a method such as reactive ion etching to form a rib waveguide 65 having a slab height of about 0.05 μm. Thereafter, an SiO ₂ film 66 is formed on the stripe pattern of the rib-type waveguide 65 by a vapor deposition apparatus or the like.

  The waveguide of the wavelength multiplexer / demultiplexer 10 may be a channel waveguide shown in FIG. In this case, the channel waveguide 67 can be formed by etching the Si core layer of the SOI substrate without leaving the slab thickness.

  FIG. 10 is a schematic configuration diagram of an optical receiver 50 including wavelength multiplexers / demultiplexers 1A to 1C (collectively referred to as “wavelength multiplexer / demultiplexer 1”). The optical receiver includes a wavelength multiplexer / demultiplexer 1, light receivers 40-1 to 40-n connected to each output (divided wavelength component) of the wavelength multiplexer / demultiplexer 1, and light receivers 40-1 to 40-1. Transimpedance amplifiers (TIAs) 42-1 to 42-n connected to 40-n. The light receiver 40 is a photodiode, for example, and converts an optical signal of each wavelength (channel) into a current signal. The TIA 42 converts the impedance of the current signal, amplifies it, and outputs it as a voltage signal. The light receiver 40 and the TIA 42 constitute an optoelectric (O / E) converter. The voltage signal obtained by the O / E conversion is supplied to the electronic logic processing circuit 60 in the subsequent stage and is subjected to signal processing. Since the optical signal output from the optical multiplexer / demultiplexer 1 has reduced crosstalk between adjacent channels, the signal quality after signal processing is also improved.

FIG. 11 is a diagram illustrating the characteristics of the wavelength multiplexer / demultiplexer according to the embodiment in comparison with the characteristics of the conventional wavelength multiplexer / demultiplexer. FIG. 11 (a) is a multiplexing / demultiplexing spectrum characteristic when the wavelength multiplexer / demultiplexer 1 of the embodiment uses the AWG 10 and AD-MRR 20 with a spacing of 400GHz and 16Ch, and FIG. It is a multiplexing / demultiplexing spectrum characteristic of the wavelength multiplexer / demultiplexer 110. In both FIG. 11A and FIG. 11B, the AWG is formed by the silicon thin wire waveguide shown in FIG. 8 or FIG. 9, the number of arrayed waveguides is 41, and the optical path length difference ΔL _Array is 12.5 μm. did. In FIG. 11A, the AD-MRR 20 of the wavelength multiplexer / demultiplexer 1 sets the radius of curvature of the ring region 23 to 4 μm and the optical coupling rate between the ring and the bus waveguide to 0.3. Thereby, a resonance characteristic with a low Q value of 1000 or less can be realized. When the propagation loss of the silicon wire waveguide is 2 dB / cm, the excess loss generated inside the AD-MRR 20 is 0.1 dB or less.

  As can be seen from FIG. 11, clear wavelength multiplexing / demultiplexing characteristics of 16 channels are obtained in both the configuration of the embodiment and the conventional configuration, but there is a significant difference in the level of crosstalk. In the wavelength multiplexer / demultiplexer of the embodiment (FIG. 11A), the crosstalk is reduced by 10 dB or more in all channels with almost no excessive loss.

  FIG. 12 is a diagram for explaining the effect of reducing the size of the array area of the AWG. In FIG. 12A, the number of AWG arrayed waveguides is reduced from 41 to 31, and the wavelength multiplexing / demultiplexing characteristics of 16 channels are plotted. FIG. 12B is a graph plotting the crosstalk for the ninth channel component when the number of arrayed waveguides is 31 in both the configuration of the embodiment and the conventional configuration as a comparative example.

  As shown in FIG. 12A, in the wavelength multiplexer / demultiplexer of the embodiment, even if the number of AWG arrayed waveguides is reduced from 41 to 31, the multiplexed / demultiplexed spectrum equivalent to that in FIG. Characteristics can be obtained. As can be seen from FIG. 12B, in the case of the conventional configuration, the crosstalk is remarkably deteriorated as the number of array waveguides is reduced. In the wavelength multiplexer / demultiplexer of the embodiment, the number of array waveguides is reduced. Can be maintained at a crosstalk level of -20 dB or lower.

  In the case of the configuration of the embodiment, by adjusting the optical coupling rate of the AD-MRR 20 (or 30) and narrowing the band, the number of AWG array waveguides can be further increased while maintaining the same level of crosstalk. Can be reduced. As a result, the wavelength multiplexing / demultiplexing device can be reduced in size and loss.

  As described above, normally, AWG tends to increase in size and insertion loss as the number of arrayed waveguides increases. Reducing the number of arrayed waveguides increases the spectral bandwidth and increases crosstalk. On the other hand, when the configuration of the embodiment is used, a desired spectral bandwidth can be maintained by reducing the number of arrayed waveguides by optimizing the filter action of the AD-MRR 20 (or 30). Therefore, loss can be reduced without sacrificing device characteristics.

FIG. 13 shows that in the embodiment, the ring circulation length L _MRR of the AD-MRR 20 (or 30) is not an integral multiple of the optical path length difference ΔL between the array waveguides of the AWG 10 (L _MRR ≠ P · ΔL _Array (P Is a graph showing the effect of adjusting a natural number)). 13A shows the combined / demultiplexed spectrum characteristics when the ring circumference is adjusted after adopting the configuration of the embodiment, and FIG. 13B shows the combined / demultiplexed spectrum characteristics of the conventional configuration of FIG. 1 as a comparative example. It is. The element parameters are the same as in the example shown in FIG. 11, but in FIG. 13, a wavelength range wider than the bandwidth corresponding to 16 channels is plotted.

In the case of the conventional configuration shown in FIG. 13B, the same transmission peak appears periodically at intervals of the FSR _AWG . On the other hand, in the case of FIG. 13A, unnecessary transmission peaks that appear periodically other than BW _DEMUX are effectively suppressed. This is because the AWG 10 and the AD-MRR 20 or 30) have different FSRs, the AWG transmission peak outside the BW _DEMUX receives a loss due to the AD-MRR 20 (or 30), and the transmittance is suppressed. FIG. 13 shows that the AWG transmission peak outside the desired band can be suppressed by 10 dB or more by controlling the ring circulation length so as not to be an integral multiple of the optical path length difference between the arrayed waveguides.

In the example of FIG. 13A, the radius of curvature of the AD-MRR is 4 μm, but the characteristic shown in FIG. 13A is that the circumference of the AD-MRR 20 (or 30) does not become an integral multiple of ΔL. This can be achieved if adjusted. Even if the radius of curvature of the AD-MRR 20 (or 30) is set to 5 μm or 6 μm, for example, the same effect can be obtained, and unnecessary transmission peaks that appear periodically other than BW _DEMUX are suppressed, and within the optical waveguide circuit Unnecessary wavelength component signals can be removed. As a result, high performance of the wavelength multiplexer / demultiplexer 1 is realized.

  As described above, in the embodiment, the AD-MRR 20 is connected to each of the output waveguides of the optical multiplexing / demultiplexing circuits 10 and 15 such as AWG, and the circulation length of each AD-MRR 20 is set to be larger than the optical path length difference of the array waveguide. A wavelength multiplexer / demultiplexer having a low power, low cross and oak spectral characteristics in a conventional manufacturing device by increasing the size and shifting from an integral multiple of the optical path length difference of the optical multiplexing / demultiplexing circuits 10 and 15. Can be manufactured.

  Further, the wavelength can be easily controlled with low power by monitoring the wavelength from the light receiver (PD1) provided in the through port of the AD-MRR 30 as shown in FIGS.

  With the configuration of the embodiment, the number of AWG array waveguides can be reduced while minimizing power consumption for wavelength control without using a high-precision manufacturing apparatus. By using the wavelength multiplexer / demultiplexer of the embodiment, an optical receiver with low loss and low crosstalk can be configured.

  The present invention can be applied to an optical multiplexing / demultiplexing device or a front end of an optical receiver.

1, 1A, 1B, 1C Wavelength multiplexer / demultiplexer 10 AWG (optical multiplexing / demultiplexing circuit)
13-1 to 13-k arrayed waveguide 15 delay interferometer type element (optical multiplexing / demultiplexing circuit)
20, 30 Add-drop type ring resonator 21, 31 Through waveguide (bus waveguide)
22, 32 Drop waveguide (bus waveguide)
23, 33 Ring region 35 Heater electrode 36 PD1 (receiver)
40 PD2 (receiver for O / E converter)
42 TIA (O / E converter current-voltage converter)
50 Optical receiver

Claims (5)

An optical multiplexing / demultiplexing circuit for multiplexing / demultiplexing optical signals of different wavelengths included in the input light;
An add / drop ring resonator optically connected to each of the plurality of outputs of the optical multiplexing / demultiplexing circuit;
The add / drop ring resonator includes a ring region, a through waveguide connected to the through port, and a drop waveguide connected to the drop port;
The resonance center wavelength of each of the add / drop type ring resonators corresponds to each of the multiplexing / demultiplexing wavelengths of the optical multiplexing / demultiplexing circuit, and the light extracted from the drop port is used as an output after wavelength separation. Wavelength multiplexer / demultiplexer. The optical multiplexing / demultiplexing circuit includes a plurality of waveguides having a predetermined optical path length difference,
2. The wavelength multiplexer / demultiplexer according to claim 1, wherein a circumference of the ring region of the add / drop ring resonator is larger than the optical path length difference of the optical multiplexing / demultiplexing circuit.   3. The wavelength multiplexer / demultiplexer according to claim 1, wherein the circumference of the ring region is not an integral multiple of the optical path length difference. A light receiving element connected to the through port of the add / drop ring resonator;
A heater electrode provided in the vicinity of the ring region;
The wavelength combination according to any one of claims 1 to 3, wherein a current or voltage applied to the heater electrode is controlled based on a current value detected by the light receiving element. Waver. The wavelength multiplexer / demultiplexer according to any one of claims 1 to 4,
A photoelectric converter connected to the drop port of the wavelength multiplexer / demultiplexer;
Including optical receiver.

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