JP2010054620A - Optical signal monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal monitor capable of detecting wavelengths and OSNR as well as optical power. <P>SOLUTION: A wedge-shaped groove 20 is formed in a first slab waveguide 12, and an optical resin is filled in the groove and a heater 30 is mounted in the groove. When an electric power is applied to the heater 30, the optical resin 21 is locally heated, changing the refractive index. By selecting the absolute value of the refractive index temperature coefficient of the optical resin 21 larger than that of quartz, an optical path length in the optical resin 21 portion varies by heating, which changes a converging position by each wavelength in the converging face of a second slab waveguide 14. In other words, the transmitting wavelength property of AWG is variable. Accordingly, with the optical signal light made incident while the heater 30 is sweep driven, and with an applied electric power determined that maximizes an output optical power, detection of a wavelength becomes possible. Also, with the optical signal light made incident while the heater 30 is sweep driven in a wider region than the wavelength component of the optical signal, and with the minimum and maximum ratio of the output optical power taken, detection of OSNR becomes possible. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an optical signal monitor mainly used for optical fiber communication. More specifically, the present invention relates to an optical signal monitor used in a WDM system that handles a plurality of optical wavelength signals.

  With an increase in communication capacity in recent years, an optical transmission system (WDM system) using wavelength division multiplexing (WDM) technology has been widely introduced from the backbone to the metro area. Each node of the WDM system monitors the optical power of the optical signal for each wavelength channel, thereby performing transmission signal quality management, system control, and the like. A conventional optical signal monitor using an arrayed waveguide grating optical multiplexer / demultiplexer (AWG) will be described with reference to FIG. An AWG composed of a first slab waveguide 12, an arrayed waveguide 13 composed of a plurality of channel waveguides having different lengths by a predetermined length, and a second slab waveguide 14. The input waveguide 11 and the output waveguide 15 are connected to each other, and these waveguides are usually produced on a silicon substrate 1 by a planar lightwave circuit (PLC) technique including a core 2 made of quartz and a clad 3. can do. When an WDM signal in which a plurality of wavelengths are combined is incident from the input waveguide 11, the AWG 10 can demultiplex and extract an optical signal for each wavelength from the output waveguide 15 (see Non-Patent Document 1). ). Furthermore, a compact optical channel monitor (OCM) has been developed that can monitor the optical power of an optical signal for each wavelength by directly mounting a photodiode (PD) 501 on the end face of each output waveguide 15 of the AWG 10. (Refer nonpatent literature 2). The PD 501 used here is an example using a chip scale package type PD array (CSP type PD array) 500 hermetically sealed in a housing 502 and a glass window 503 (see Non-Patent Document 3). . The light receiving surface of each PD 501 built in the CSP type PD array 500 is mounted optically coupled to each of the output waveguides 15 of the AWG 10.

Japanese Patent No. 3436937 Japanese Patent No. 3498650 Takahashi et al., “Array waveguide diffraction grating for WDM”, NTT R & D, Vol. 46, no. 7, pp. 685-692, 1997 Oyama et al., “40-ch optical power channel monitor module using AWG and CSP type PD array”, 2006 IEICE Electronics Society Conference Proceedings 1, C-3-78, pp. 200 Doi et al., “Development of Chip Scale Package Type PD Array (CSP-PD)”, IEICE Technical Report EMD2007-36, CPM2007-57, OPE2007-74, LQE2007-3, (2007-08), pp. 39-44

  One method for increasing the capacity of a WDM system is to narrow the channel frequency interval. The narrower the frequency interval, the more severe the wavelength accuracy required in the system. Therefore, an optical signal monitor used in the WDM system is required to have a function for detecting not only the optical power but also the wavelength and the optical signal intensity ratio (OSNR).

  However, the optical signal monitor using the AWG according to the prior art described above has a problem that only the optical power of the demultiplexed optical signal can be detected.

  The present invention has been made in view of the problems that have arisen in the prior art. The purpose of the present invention is to implement a function of detecting a wavelength and an optical signal intensity ratio (OSNR) in addition to the detection of optical power. It is to provide an optical signal monitor.

  In order to solve such a problem, the invention according to claim 1 is directed to an optical signal monitor that demultiplexes input wavelength-division multiplexed light and outputs a plurality of lights having different wavelengths. A plurality of channel waveguides for demultiplexing the wavelength-multiplexed light by a change in wavelength due to a phase difference generated between the plurality of channel waveguides, and arranged so as to intersect the traveling direction of the light, It is characterized by comprising a material that changes the phase difference with respect to light of a wavelength according to temperature, a mechanism for heating or cooling the material, and one or a plurality of photodiodes arranged at an output portion.

  The invention according to claim 2 is the array waveguide diffraction grating constituted by the plurality of channel waveguides having different lengths by a predetermined length according to claim 1, and the array waveguide diffraction grating. And an input side slab waveguide disposed between the arrayed waveguide diffraction grating and the plurality of output channel waveguides. Each of the waveguides is composed of an upper clad, a core, and a lower clad, and the slab waveguide on the input side or the output side is arranged on the input side with respect to the input light of each wavelength. A groove formed by bending the material that changes the phase difference generated between the path from the slab waveguide to the slab waveguide on the previous output side through a plurality of channel waveguides so as to intersect the light traveling direction Including filling The groove is formed by removing the upper cladding and the core from the input-side or output-side slab waveguide, or from the input-side or output-side slab waveguide, the upper cladding, the core, and the core The material is formed by removing the lower cladding, and the material is a material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of a slab waveguide including the material.

  The invention according to claim 3 is the invention according to claim 2, wherein the groove is a plurality of grooves formed in the input-side or output-side slab waveguide for filling the material. The grooves are grouped, and a mechanism for independently heating or cooling the material is provided for each group.

According to a fourth aspect of the present invention, in the first aspect, the arrayed waveguide diffraction grating composed of the plurality of channel waveguides having different lengths by a predetermined length, and the arrayed waveguide diffraction grating And an input side slab waveguide disposed between the arrayed waveguide diffraction grating and the output channel waveguide, and an output slab waveguide disposed between the arrayed waveguide grating and the output channel waveguide. Each of the waveguides includes an upper clad, a core, and a lower clad, and a groove is formed across the arrayed waveguide diffraction grating, and the groove extends from the channel waveguide to the upper clad and It is formed by removing the core or by removing the upper cladding, the core, and the lower cladding from the channel waveguide, and the groove has the It said material having a temperature coefficient different from the refractive index temperature coefficient of the effective refractive index of the channel waveguide is characterized in that it is filled.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the groove is a plurality of grooves for filling the material formed across the plurality of channel waveguides constituting the arrayed waveguide diffraction grating. The plurality of grooves are grouped, and a mechanism for independently heating or cooling the second material is provided for each group.

  According to a sixth aspect of the present invention, in the first aspect, the plurality of channel waveguides include an upper cladding, a core, and a lower cladding, and N + 1 (N is an integer equal to or greater than 1). N sets of arm waveguides sandwiched between an optical coupler and an adjacent optical coupler, and each of the N sets of arm waveguides includes a first arm waveguide and a second arm waveguide having different optical path lengths. And a groove is formed in at least one of the first arm waveguide or the second arm waveguide, and the groove removes the upper cladding and the core from the arm waveguide in which the groove is formed. Formed by removing the upper clad, the core, and the lower clad from the arm waveguide in which the groove is formed, and the arm in which the groove is formed The material having the refractive index temperature coefficient different from the temperature coefficient of the effective refractive index of the waveguide is filled.

  According to a seventh aspect of the present invention, in the first aspect, the plurality of channel waveguides are configured by an upper cladding, a core, and a lower cladding, and are configured by connecting one or more optical branching couplers. Each of the first optical branching couplers having outputs of M (M is an integer of 2 or more) ports and one or a plurality of optical branching couplers connected to each other. M delay waveguides, each having a different amount of delay, are provided between each of the second optical branch couplers having the same number of input ports as the number of output ports of the optical branch coupler. A groove is formed in a part of at least one of the M delay waveguides, and the groove is formed by removing the upper cladding and the core from the delay waveguide in which the grooves are formed. Or the groove is formed A refractive index temperature coefficient different from the temperature coefficient of the effective refractive index of the delay waveguide in which the groove is formed, wherein the groove is formed by removing the upper cladding, the core, and the lower cladding from the delay waveguide. It is filled with the said material which has.

  The invention according to claim 8 is the invention according to claim 1, wherein the plurality of channel waveguides are a circular ring waveguide and one or two input / output waveguides. An upper clad, a core, and a lower clad, wherein the ring waveguide is obtained by removing the upper clad and the core from the ring waveguide or from the ring waveguide, the upper clad, the core, And a groove formed by removing the lower clad, wherein the groove is filled with the material having a refractive index temperature coefficient different from the temperature coefficient of the effective refractive index of the ring waveguide. And

  According to the present invention, it is possible to realize an optical signal monitor that measures OSNR and peak wavelength by providing a plurality of PDs at the output part of a wavelength tunable filter whose phase is changed by locally heating an optical interference circuit. Can do.

(First embodiment)
FIG. 2 shows a first embodiment. FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. In the AWG composed of a waveguide made of quartz as in the prior art, unlike the conventional example, a wedge-shaped groove 20 is formed in the first slab waveguide 12, and an optical resin is filled in the groove, Further, there is a feature that a heater 30 for locally heating the optical resin 21 is mounted. The refractive index temperature coefficient of the optical resin used here is different from that of quartz. Specifically, with respect to the refractive index temperature coefficient of the quartz ^{+ 1.1 × 10 -5 [1 /} ℃], the refractive index temperature coefficient, a silicone resin of ^{-37 × 10 -5 [1 / ℃} ], optical It used as resin (refer patent document 1).

  In order to reduce the radiation loss due to the groove 20, the groove 20 is usually divided into a plurality of parts. Furthermore, in order to cancel the change of the equiphase surface of the light of each wavelength caused by the environmental temperature change, the shape of the groove formed in the slab waveguide is such that the traveling direction of the light propagating through the slab waveguide is The grooves are arranged in a curved shape so that the light refraction angle is always uniform.

  Actually, an AWG was produced as follows. A quartz optical waveguide composed of a core and a clad with a relative refractive index difference of 1.5% was formed on a silicon substrate by PLC technology. The size of the core is 4.5 μm × 4.5 μm. Then, the groove | channel filled with optical resin was processed by RIE. The width of the groove was formed to be curved while changing from 7 μm to 60 μm. The number of grooves is divided into six, and the interval between the grooves is constant at 40 μm. Here, the depth of the groove was etched to a position deeper than the core.

  A photodiode (PD) 501 is directly mounted on the end face of each output waveguide 15 of the AWG 10. Here, an example in which a CSP type PD array 500 is used is shown, and the light receiving surface of each PD 501 incorporated therein is mounted optically coupled to each of the output waveguides 15 of the AWG 10.

  Now, when electric power is applied to the heater 30, the optical resin 21 is locally heated and its refractive index changes. Since the absolute value of the refractive index temperature coefficient of the optical resin 21 is larger than that of the waveguide made of quartz, the optical path length in the optical resin 20 portion is changed by heating, and as a result, the second slab waveguide 14 of the AWG 10 changes. The condensing position for each wavelength changes on the condensing surface. This means that the transmission wavelength characteristic of the AWG can be made variable.

  In addition, the heater 30 shown in the drawing shows an approximate outer shape, and may actually be an external heater that can locally heat the optical resin. Further, an electrical wiring 40 for applying electric power is taken out from the heater 30.

  FIG. 4 shows transmission wavelength characteristics with respect to applied power of an AWG 201 manufactured by mounting a ceramic heater as the heater 30 on the AWG 10 with a frequency interval of 100 GHz on the groove 20 filled with the optical resin 21. It can be seen that the transmission wavelength characteristic of the AWG 201 is variable without being deformed in proportion to the applied power. Since the applied power on the horizontal axis can be associated with the peak wavelength, the transmission wavelength of the AWG can be easily made variable simply by providing the AWG 10 with means for locally heating the optical resin 21. In this example, the transmission wavelength variable efficiency with respect to the applied power was about 5 [GHz / W]. This can be further improved by optimizing the shape of the heater 30 and its mounting form.

  Thus, since the transmission wavelength characteristic corresponds to the applied power to the heater 30, the optical signal light is incident while sweeping the heater 30 of the AWG 201, and the applied power that maximizes the optical power output at that time is obtained. Knowing it makes it possible to detect the wavelength. In addition, the OSNR is detected by taking the optical signal light in a wider range than the wavelength component of the optical signal while making the heater of this AWG201 sweep drive, and taking the minimum and maximum ratio of the optical power output at that time. It becomes possible to do.

In more detail, the operation of the optical signal monitor 200 according to this configuration will be described below. When a WDM signal obtained by combining a plurality of wavelength signals is input from the input waveguide 11 of the AWG 10, each wavelength signal is output for each output waveguide 15 according to the operation principle of the AWG. The light is received by the PD 501 and converted into an electrical signal and output. At this time, when electric power is applied to the heater 30, the optical resin 21 filled in the groove 20 is heated, and the transmission wavelength characteristics of the AWG 10 move as described above. At this time, the applied power to the heater 30 may be such that the movable range of the transmission characteristics of the AWG 10 can be swept within a range narrower than the transmission band of each adjacent channel. FIG. 5A shows how the optical signal 700 transmitted through each channel is monitored while the heater 30 is driven. When electric power is applied to the heater 30, the transmission characteristic 701 of the AWG 10 is moved in proportion to it (arrow in the figure), and the corresponding photocurrent, ie, the monitor signal 702 from the PD 501 is output (FIG. 5B). Power applied to the heater 30, it is possible to associate to the wavelength (lambda) information, applied power i.e. wavelength position monitor signal 702 becomes the peak (lambda ₁₎ is, as the wavelength of the optical signal coming transmitted through the channel It can be detected. In addition, the peak value (P ₁ ) of the vertical axis power (P) can be detected as the optical power of the optical signal 700. Furthermore, the ratio of the value of the peak value of the monitor signal 702 (P ₁₎ and the monitor signal of the noise level (P _N) may be detected as OSNR. Thus, in addition to the optical power, the optical signal monitor, which can only detect the optical power with the conventional technology, is configured by varying the transmission wavelength characteristic of the AWG in this embodiment, Wavelength and OSNR can be monitored.

  Here, as a feature of using the AWG, the sweep variable range of the transmission wavelength characteristic may be a range that can be driven with an applied power that has a variable range equal to or smaller than the adjacent channel frequency interval of the AWG. This is because the AWG can simultaneously output optical signals of respective channel frequencies (that is, wavelengths) for each output waveguide. Therefore, the optical signal monitor according to the present embodiment has a feature that all the optical signals of the wavelength channels can be collectively monitored by driving the sweep wavelength variable range narrower than the transmission band of each channel. This is characterized in that the reading speed is higher than that of an optical signal monitor that sweeps the variable filter over the entire wavelength range on the system.

  Note that by designing the transmission bandwidth of the AWG 10 to be narrower, the waveform of the optical signal can be monitored with higher accuracy. That is, it is possible to monitor the waveform due to the difference in the bit rate of the modulated optical signal and the difference in the modulation format.

  As described above, the present invention is characterized in that, by mounting the CSP type PD array 500, it is possible to construct a temperature-independent OPM that is unprecedented in compactness and does not vary in monitor characteristics with respect to environmental temperature. .

  In the present embodiment, an example in which a ceramic heater is used as the heater 30 is shown, but it goes without saying that the type is not selected as long as mounting is possible with a mechanism capable of locally heating. For example, a Peltier element, a sheet heater, a resistance heating element, or the like may be used. Conversely, a mechanism capable of locally cooling may be implemented. If possible, it is desirable to use a small heating mechanism or cooling mechanism that maximizes the variable filter characteristics with respect to the applied power.

  In order to further increase the efficiency of the variable characteristic of the transmission wavelength with respect to the applied power, a second waveguide material (this book) that is replaced in the first waveguide material (quartz in this embodiment) and locally heated or cooled. In the embodiment, the absolute value of the refractive index temperature coefficient of the silicone resin) is preferably larger than that of the first waveguide material. Further, the place where the second waveguide material is heated or cooled may be a part of the second waveguide material or the entire second waveguide material. This is also true for the embodiments described below.

  In the present embodiment, the example in which the heater 30 for locally heating the optical resin 21 filled in the groove 20 formed in the first slab waveguide 12 is mounted has been described. For example, as shown in FIG. 6, a groove 20 may be formed in the second slab waveguide 14, and a heater 31 for locally heating the filled optical resin 21 may be mounted, or FIG. As shown in FIG. 8, a groove 20 may be formed in the portion of the arrayed waveguide 13, and a heater 30 for locally heating the filled optical resin 21 may be mounted. Alternatively, as shown in FIG. A groove 20 may be formed in both the first slab waveguide 14 and the second slab waveguide, and a heater 30 for locally heating the filled optical resin 21 may be mounted. Can produce the same effect of the invention It is needless to say that the ability. This is the same in the embodiments described below.

  Also, here, the first waveguide material has a positive refractive index temperature coefficient, and the second waveguide material has a negative refractive index temperature coefficient. As described above in combination, the first waveguide material has a positive refractive index temperature coefficient, and the second waveguide material also has a positive refractive index temperature coefficient, if other materials are possible. Alternatively, a combination in which the first waveguide material has a negative refractive index temperature coefficient and the second waveguide material also has a negative refractive index temperature coefficient may be used. That is, it is only necessary that the refractive index temperature coefficients of the first waveguide material and the second waveguide material are different. In order to maximize the transmission wavelength variable efficiency with respect to the applied power, it is desirable that the absolute value of the refractive index temperature coefficient of the second waveguide material be larger than that of the first waveguide material. This is also true for the embodiments described below.

  In addition, as a constituent material for filling the groove, various optical resins such as silicone resin, epoxy resin and polymethyl methacrylate resin, or multi-component glass materials containing sodium, potassium and calcium are used. In many cases, a quartz-based material is used as a constituent material of the channel waveguide constituting the output slab waveguide, the input / output channel waveguide, and the arrayed waveguide diffraction grating.

  Further, in order to reduce the radiation loss due to the groove 20, the groove 20 is preferably divided into a plurality of parts. However, this is not the case when radiation loss is not a concern.

  When the groove for filling the optical resin 21 in the slab waveguide is formed, the light emitted from the input waveguide propagates near the center of the slab waveguide and passes through the groove filled with the optical resin. The refraction angle differs from the refraction angle when propagating through a portion away from the center of the slab waveguide and passing through the groove filled with the optical resin, resulting in aberration, and as a result, transmission of the AWG. Degrading properties. Therefore, the shape of the groove formed in the slab waveguide is such that the traveling direction of light propagating through the slab waveguide is curved so that the refraction angle of light is always uniform in the groove. Since it is possible to cancel the change in the equiphase plane of the light of each wavelength that occurs with the temperature change, it is possible to obtain optimized transmission characteristics of the AWG (see Patent Document 2).

  Further, the depth of the groove may be etched beyond the lower surface of the core. This is also true for the embodiments described below.

(Second embodiment)
FIG. 9 shows a second embodiment. FIG. 10 is a cross-sectional view taken along the line BB ′ of FIG. The difference from the first embodiment is that a thin film heater 32 is integrated as a heater 30 on the periphery of the groove 21 and on the clad 3 between the grooves 21 by a microfabrication process. By using the thin film heater 32, the mounting process of the external heater 30 performed in the first embodiment can be eliminated, and the increase in the thickness direction due to the heater mounting can be eliminated. Can be achieved. Examples of the material of the thin film heater 32 include chromium and titanium, but are not limited to these materials.

  The actually produced AWG is the same as in the first embodiment. Furthermore, the width of the heater integrated on the clad between the grooves was 20 μm.

  As described above, according to the present embodiment, in the conventional temperature-independent AWG, the heater can be integrated in the region filled with the optical resin by the microfabrication technique. The heater mounting process can be eliminated, and an AWG having a variable transmission wavelength can be easily manufactured.

  FIG. 11 shows the center transmission frequency characteristics with respect to the applied power of the AWG produced by integrating the thin film heater 32 as the heater 30 in the AWG 10 having a frequency interval of 100 GHz. From this figure, it can be seen that the variable efficiency of the transmission wavelength characteristic with respect to the applied power is about 10 [GHz / W]. Since the heater position can be reliably integrated in the immediate vicinity of the groove 20 filled with the optical resin 21 by the microfabrication technique, the variable efficiency of the transmission wavelength characteristic with respect to the applied power is compared with the first embodiment. It can be seen that can be improved.

  Further, as described in the first example, this embodiment may be realized in the second slab waveguide 14 or in the arrayed waveguide 13. This is also true for the embodiments described below.

  Furthermore, as a measure for improving the variable efficiency of the transmission wavelength characteristic with respect to the applied power, the heating area is densely localized by increasing the number of divisions of the groove 20 and increasing the area where the thin film heater 32 can be integrated. Further improvement can be achieved. This is also true for the embodiments described below.

  A connection pattern of the thin film heater 32 shown in FIG. 12 will be described. FIG. 12 shows a pattern of grooves and thin film heaters extracted. Thus, a pattern in which the thin film heaters 32 are connected in parallel as shown in FIG. 12A may be used, or a pattern in which the thin film heaters 32 are connected in series as shown in FIG. Alternatively, as shown in FIG. 12C, a connection in which a parallel connection and a series connection are mixed may be used, and the present invention is not limited to these. Further, the thin film heater does not always have to be arranged on the clad between the grooves, and may be arranged at intervals as needed. If possible, it is desirable to integrate the heaters in a pattern that maximizes the variable efficiency of the transmission wavelength characteristic with respect to the applied power. This is also true for the embodiments described below.

(Third embodiment)
FIG. 13 shows a third embodiment. FIG. 14 is a cross-sectional view taken along the line CC ′ of FIG. The difference from the second embodiment is that the thin film heater 32 is integrated on the bottom of the groove 20 by a microfabrication process. Heat generated from the thin film heater 32 in the second embodiment is conducted to the optical resin 21 filled in the groove 20 through the clad 3 once. On the other hand, according to the present embodiment, since the optical resin 21 is filled directly on the thin film heater 32, the heat generated from the thin film heater 32 is directly conducted to the optical resin 21. Therefore, the variable efficiency of the transmission wavelength characteristic with respect to the applied power can be increased as compared with the second embodiment. Further, as a measure for improving the variable efficiency of the transmission wavelength characteristic with respect to the applied power, the heating region is densely localized by increasing the number of divisions of the grooves 20 and increasing the number of grooves 20 in which the thin film heaters 32 can be integrated. By doing so, further improvement can be achieved. If possible, a heater may also be integrated on the side wall of the groove 20.

(Fourth embodiment)
FIG. 15 shows a fourth embodiment. In the present embodiment, unlike the embodiments described above, the first slab waveguide 12 is characterized by the arrangement of the grooves 20 that fill the optical resin 21. That is, when the wedge-shaped groove formed in the above-described embodiment is called a first groove portion, the second groove portion is formed in the direction opposite to the first groove portion, and the first groove portion and the second groove portion are formed. The heater 32 is also integrated around the groove portion so that the optical resin filled in each groove can be heated. The heater disposed around the first groove 121 is referred to as a first heater 131, and the heater disposed around the second groove 122 is referred to as a second heater 132. However, the first heater 131 and the second heater 132 need to have electrical wirings 40 and 41 that can apply power independently of each other. By arranging the second heater 132, the optical resin 21 filled in the second groove 122 also changes the optical path length in order to change the refractive index by heating. As a result, the second slab waveguide 14 of the AWG 10 is changed. The condensing position of each wavelength changes on the condensing surface. However, since the second groove 122 is in the opposite direction with respect to the first groove 121, the condensing surface of the second slab waveguide 14 obtained by heating the optical resin 21 filled in the first groove 121. Acts in the opposite direction to the light condensing direction. By applying this point, the first heater 131 is usually driven to make the transmission wavelength characteristic variable, and the second heater 132 is separately driven to increase the transmission wavelength characteristic variable speed. It becomes possible to control. That is, by driving a control circuit between the first heater 131 and the second heater 132, the sweep speed of the wavelength tunable filter can be varied, or high-speed tuning can be performed to an arbitrary transmission wavelength characteristic point. It becomes possible.

  Here, although the configuration example in which the groove 20 is divided is shown, it is not always necessary to divide the groove 20, but it is possible to reduce the radiation loss by dividing the groove, and the heater is densely integrated locally. As a result, the variable efficiency of the transmission wavelength characteristic can be increased. Moreover, if each groove | channel 20 which comprises a 1st groove part and each groove | channel 20 which comprises a 2nd groove part mount the mechanism which drives the 1st heater 131 and the 2nd heater 132 independently, Each groove pattern may be arranged alternately or in a plurality.

  Further, the arrangement (grouping) of the first groove 121 and the second groove 122 can be variously arranged. That is, as shown in FIG. 15, both the first groove 121 and the second groove 122 are disposed in the first slab waveguide 12, and the second groove 122 is disposed on the input waveguide 11 side. Alternatively, both the first groove portion 121 and the second groove portion 122 may be disposed in the first slab waveguide 12 and the first groove portion may be disposed on the input waveguide 11 side. Furthermore, both the first groove part 121 and the second groove part 122 may be arranged in the second slab waveguide 14 and the second groove part 122 may be arranged on the output waveguide 15 side. Both the groove 121 and the second groove 122 may be disposed in the second slab waveguide 12 and the first groove may be disposed on the output waveguide 15 side. Further, the first groove 121 may be disposed in the first slab waveguide 12 and the second groove 122 may be disposed in the second slab waveguide 14. Conversely, the first groove 121 may be disposed. The second slab waveguide 14 may be disposed in the second slab waveguide 14, and the second groove 122 may be disposed in the first slab waveguide 12. Further, the first groove 121 and the second groove 122 may be arranged in the portion of the arrayed waveguide 13. Further, if possible in layout, the grooves 20 constituting the first groove 121 and the grooves 20 constituting the second groove 122 may be interwoven and arranged. However, since the first heater 131 and the second heater 132 are driven independently, the first groove 121 and the second groove 122 are arranged separately from each other in order to reduce thermal interference between them. It is desirable to dispose each of the first slab waveguide 12 and the second slab waveguide 14.

(Fifth embodiment)
FIG. 16 shows a fifth embodiment. This embodiment is different from the previous embodiment in that the CSP-PD array is attached to the end face of the second slab 14. By doing so, the output waveguide portion can be eliminated, so that it is possible to further reduce the size of the optical signal monitor. The heater is not particularly limited to this form.

(Sixth embodiment)
FIG. 17 shows a sixth embodiment. This is a Mach-Zehnder optical interference circuit composed of a first optical coupler 60, a second optical coupler 61, and a first arm waveguide 62 and a second arm waveguide 63 that connect the two optical couplers. It is. In the present embodiment, an example in which the first and second optical couplers are configured by directional couplers is shown. Further, the length of the first arm waveguide is different from the length of the second arm waveguide, and the length of the first arm waveguide is longer than the length of the second arm waveguide. In the Mach-Zehnder optical interference circuit formed of the first waveguide material, a groove 20 is formed in a part of the first arm waveguide, and a second waveguide material different from the first waveguide material is formed. Fill there. For example, quartz having a refractive index temperature coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] as the first waveguide material, and a refractive index temperature coefficient α ₂ as the second waveguide material. However, a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.] is used.

  In the above configuration, the thin film heater 32 is integrated around the groove in order to locally heat the optical resin 21 filled in the groove 20. When electric power is applied to this heater, a Mach-Zehnder optical interference circuit with variable transmission wavelength characteristics can be realized. An example of calculating the transmission characteristics is shown in FIG. That is, according to the present embodiment, it is possible to provide a Mach-Zehnder optical interference circuit having a variable transmission wavelength characteristic.

  Further, the PD 501 is attached to the output waveguide end face of the Mach-Zehnder optical interference circuit. Here, when the transmission wavelength characteristic is swept by heater heating, a photocurrent, that is, a monitor signal is output from the PD 501 accordingly. The operation here is as described in the first embodiment. Thus, it is possible to configure an optical signal monitor that detects not only the optical power but also the wavelength and OSNR by sweeping the transmission wavelength characteristic.

  As a heater integration method, the heater 31 may be attached externally as described in the first embodiment, or a thin film is formed on the clad 3 around the groove as described in the second embodiment. The heater 32 may be integrated, or as described in the third embodiment, the thin film heater 32 may be integrated at the bottom of the groove 20, and there is no restriction on its implementation. Needless to say, a cooling mechanism may be used instead of a heating mechanism such as a heater.

  Also here, the configuration example in which the groove is divided is shown. However, although it is not always necessary to divide the groove, it is possible to reduce the radiation loss by dividing the groove. Further, as shown in FIG. 19, a groove for the same optical path length is formed in the first arm waveguide filled with the optical resin on the second arm waveguide side, and the groove is formed by filling the optical resin. The loss between both arm waveguides due to the formation of may be made uniform.

(Seventh embodiment)
FIG. 20 shows a seventh embodiment. This is an M-stage lattice optical interference circuit in which arm waveguides of Mach-Zehnder optical interference circuits are connected in M-stage columns. Further, the M-stage lattice optical interference circuit includes M + 1 optical couplers and M delay units disposed between adjacent ones of the optical couplers, and the delay units include the first arm waveguide and the first optical waveguide. The length difference between the first arm waveguide and the second arm waveguide is set to ΔL.

In this lattice optical interference circuit formed of the first waveguide material, a groove is formed in a part of the first arm waveguide, and a second waveguide material different from the first waveguide material is formed therein. Filled. Here, quartz having a refractive index temperature coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and the refractive index temperature coefficient α is used as the second waveguide material. ₂ uses a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.].

  The transmission spectrum of the M-stage lattice optical interference circuit is expressed by the following equation.

Here, M is the number of stages, xq is the amplitude coefficient, ΔL is the optical path length difference between the arm waveguides, f is the optical frequency, and c is the speed of light. (M = 1 corresponds to the one-stage Mach-Zehnder optical interference circuit described in the sixth embodiment.)

  In the above configuration, a thin film heater is integrated around the groove formed in the first arm waveguide in order to locally heat the optical resin filled in the groove. By applying electric power to this heater, a lattice type optical circuit with variable transmission wavelength characteristics was realized. The transmission wavelength characteristics are shown in FIG. That is, according to the present embodiment, it is possible to provide a lattice optical interference circuit having a variable transmission wavelength characteristic.

  Further, the PD 501 is attached to the output waveguide end face of the M-stage lattice optical interference circuit. Here, when the transmission wavelength characteristic is swept by heater heating, a photocurrent, that is, a monitor signal is output from the PD 501 accordingly. The operation here is as described in the first embodiment. Thus, it is possible to configure an optical signal monitor that detects not only the optical power but also the wavelength and OSNR by sweeping the transmission wavelength characteristic.

  In this embodiment, the optical path length differences of the first to Mth delay units are all set to ΔL, but the optical path length difference may be changed for each delay unit.

  Also here, the configuration example in which the groove is divided is shown. However, although it is not always necessary to divide the groove, it is possible to reduce the radiation loss by dividing the groove. Further, as shown in FIG. 22, a groove having the same optical path length as that of the first arm waveguide filled with the optical resin is formed on the second arm waveguide side, and the groove is formed by filling the optical resin. The loss between both arm waveguides due to the formation of may be made uniform.

(Eighth embodiment)
FIG. 23 shows an eighth embodiment. This is an M-stage transversal optical interference circuit in which arm waveguides of a Mach-Zehnder optical interference circuit are connected in M stages in parallel. The M-stage transversal optical interference circuit includes an optical coupler (corresponding to the first optical branching coupler) that demultiplexes an input into M waveguides, and M arm waveguides (delayed waveguides) connected to the optical coupler. And an optical coupler (corresponding to the second optical branching coupler) for multiplexing the M arm waveguides. The optical path length differences of the second to M-th arm waveguides with respect to the first arm waveguide are set to ΔL + φ ₂ , 2ΔL + φ ₃ ,... (M−1) ΔL + φ _M , respectively. Here, φ _M is the phase of the Mth arm waveguide.

In the transversal optical interference circuit formed of the first waveguide material, a groove is formed in a part of the first to (M−1) -th arm waveguides, and the second is different from the first waveguide material. The waveguide material was filled there. Here, as the first waveguide material, the refractive index temperature coefficient alpha ₁ is a quartz ^{+ 1.1 × 10 -5 [1 /} ℃], also as the second waveguide material, the refractive index temperature coefficient alpha ₂ used a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.].

  The transmission spectrum of the M-stage transversal optical interference circuit is expressed by the following equation.

Here, M is the number of stages, xq is the amplitude coefficient, ΔL is the optical path length difference between the arm waveguides, f is the optical frequency, and c is the speed of light.

  In the above configuration, in order to locally heat the optical resin filled in the groove, the thin film heater is integrated around the groove formed in the first to M-1th arm waveguides. By applying power to this heater, a transversal optical interference circuit with variable transmission wavelength characteristics was realized.

  Further, the PD 501 is attached to the output waveguide end face of the M-stage transversal optical interference circuit. The PD 501 may be mounted with a single-channel CSP type PD array 500, but the form is not particularly limited. That is, the aforementioned GSP-PD array may be used.

  Here, when the transmission wavelength characteristic is swept by heater heating, a photocurrent, that is, a monitor signal is output from the PD 501 accordingly. The operation here is as described in the first embodiment. Thus, it is possible to configure an optical signal monitor that detects not only the optical power but also the wavelength and OSNR by sweeping the transmission wavelength characteristic.

  Also here, the configuration example in which the groove is divided is shown. However, although it is not always necessary to divide the groove, it is possible to reduce the radiation loss by dividing the groove. Furthermore, as shown in FIG. 24, it is also possible to make the loss between the arm waveguides uniform by forming grooves for the same optical path length in all the arm waveguides and filling with optical resin. Desirably, the groove for equalizing the loss should be formed away from the heater integrated portion.

(Ninth embodiment)
FIG. 25 shows a ninth embodiment. This is 1 × 2 ^M filter connecting the Mach-Zehnder interferometer circuit 1 input 2 output M stage, in multiple stages. Optical path length difference of the Mach-Zehnder interferometer circuit in the m-th stage, 2 ^Mm · ΔL + φm, is set to k. Where φm, k is the phase of the kth element among the mth elements. For example, in the configuration of FIG.
The optical path length difference between the first and first elements is 4ΔL + φ1,1
The optical path length difference between the second stage and the first element is 2ΔL + φ2,1
The optical path length difference between the second and second elements is 2ΔL + φ2,2
The optical path length difference between the third stage and the first element is ΔL + φ3,1
The optical path length difference between the third and second elements is ΔL + φ3,2
The optical path length difference between the third and third elements is ΔL + φ3,3
The optical path length difference between the third and fourth elements is ΔL + φ3,4
Here, φ1,1 = 0, φ2,1 = π / 2, φ2,2 = 0, φ3,1 = π / 4, φ3,2 = 3π / 4, φ3,3 = π / 2, φ3,4 FIG. 26A shows the transmission wavelength characteristic when = 0 is set.

In the present 1 × 2 ^M filter formed of the first waveguide material, a groove is formed in a part of the arm waveguide, and a second waveguide material different from the first waveguide material is filled therein. . Here, quartz having a refractive index temperature coefficient α ₁ of + 1.1 × 10 ⁻⁵ [1 / ° C.] is used as the first waveguide material, and the refractive index temperature coefficient α _{2 is} used as the second waveguide material. However, a silicone resin of −37 × 10 ⁻⁵ [1 / ° C.] was used.

  In the above configuration, the thin film heater is integrated around the groove in order to locally heat the optical resin filled in the groove.

As described above, the transmission wavelength characteristics of the input port 1 and the output port 1 when the optical resin filled in the groove is locally heated are shown in FIG. By applying power to the heater, a Mach-Zehnder optical interference circuit type 1 × 2 ^M filter having variable transmission wavelength characteristics can be realized.

Further, the PD 501 is attached to the output waveguide end face of the Mach-Zehnder optical interference circuit type 1 × 2 ^M filter. The PD 501 may be mounted with a single-channel CSP type PD array 500, but the form is not particularly limited. That is, the multi-channel CSP-PD array described above may be used. The output port to which the PD is attached depends on the design of the Mach-Zehnder optical interference circuit type 1 × 2 ^M filter.

  Here, when the transmission wavelength characteristic is swept by heater heating, a photocurrent, that is, a monitor signal is output from the PD 501 accordingly. The operation here is as described in the first embodiment. Thus, it is possible to configure an optical signal monitor that detects not only the optical power but also the wavelength and OSNR by sweeping the transmission wavelength characteristic.

  Also here, the configuration example in which the groove is divided is shown. However, although it is not always necessary to divide the groove, it is possible to reduce the radiation loss by dividing the groove. Furthermore, as shown in FIG. 27, a groove for the same optical path length may be formed for each pair of arm waveguides, and the loss between the arm waveguides may be made uniform by filling with optical resin.

Here, in the configuration described above, 1 × as an element constituting of 2 ^M filter, was used Mach-Zehnder interferometer, it may be used Lattice beam interferometer and transversal beam interferometer as described above, Other optical interference circuits such as a ring optical interference circuit described later may be used, or a plurality of different optical interference circuits may be used.

(Tenth embodiment)
FIG. 28 shows a tenth embodiment. This is a ring resonator 80 having directional couplers 72 between the waveguide 70 and the ring waveguide 71 at two locations. The ring resonator 80 exhibits a steep transmission wavelength characteristic with respect to the input from the input port S1, depending on the length of the ring waveguide, in the output characteristic from the output port S2. Further, the PD 501 is integrated at the output port S2 of the ring resonator 80. The PD 501 may be mounted with a single-channel CSP type PD array 500, but the form is not particularly limited. By locally heating the optical resin 21 filled in the groove 20 formed in a part of the ring waveguide 71, the resonance frequency (wavelength) can be made variable. When the transmission wavelength characteristic is swept by heating the heater, a photocurrent from the PD 501, that is, a monitor signal 702 is output accordingly. By sweeping the transmission wavelength characteristic, not only the optical power but also the wavelength and OSNR can be detected.

It is a figure which shows the conventional optical signal monitor using an array waveguide diffraction grating type | mold optical multiplexer / demultiplexer (AWG). It is a figure which shows the optical signal monitor which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. 2. It is a figure which shows the transmission wavelength characteristic with respect to the applied electric power of the optical signal monitor which concerns on 1st Embodiment. It is a figure which shows a mode that the optical signal which permeate | transmits each channel is monitored, driving a heater in the optical signal monitor which concerns on 1st Embodiment. It is a figure which shows the modification of the optical signal monitor which concerns on 1st Embodiment. It is a figure which shows the modification of the optical signal monitor which concerns on 1st Embodiment. It is a figure which shows the modification of the optical signal monitor which concerns on 1st Embodiment. It is a figure which shows the optical signal monitor which concerns on 2nd Embodiment. FIG. 10 is a cross-sectional view taken along line B-B ′ of FIG. 9. It is a figure which shows the center transmission frequency characteristic with respect to the applied electric power of the optical signal monitor which concerns on 2nd Embodiment. It is a figure which extracts and shows the pattern of a groove | channel and a thin film heater. It is a figure which shows the optical signal monitor which concerns on 3rd Embodiment. FIG. 15 is a cross-sectional view taken along line C-C ′ of FIG. 14. It is a figure which shows the optical signal monitor which concerns on 4th Embodiment. It is a figure which shows the optical signal monitor which concerns on 5th Embodiment. It is a figure which shows the optical signal monitor which concerns on 6th Embodiment. It is a figure which shows an example which calculated the transmission characteristic about the optical interference circuit which concerns on 6th Embodiment. It is a figure which shows the modification of the optical signal monitor which concerns on 6th Embodiment. It is a figure which shows the M stage lattice optical interference circuit which concerns on 7th Embodiment. It is a figure which shows the transmission wavelength characteristic of the lattice optical interference circuit which concerns on 7th Embodiment. It is a figure which shows the deformation | transformation form of the M stage lattice optical interference circuit which concerns on 7th Embodiment. It is a figure which shows the M stage transversal optical interference circuit which concerns on 8th Embodiment. It is a figure which shows the modification of the M stage transversal optical interference circuit which concerns on 8th Embodiment. It is a diagram illustrating a 1 × 2 ^M filter according to the ninth embodiment. It is a figure which shows the transmission characteristic of the 1 * 2 ^M filter which concerns on 9th Embodiment. It is a figure which shows the deformation | transformation form of the 1 * 2 ^M filter which concerns on 9th Embodiment. It is a figure which shows the optical signal monitor which concerns on 10th Embodiment.

Explanation of symbols

1 substrate 2 core 3 clad (corresponding to upper clad and lower clad)
10 AWG (compatible with wavelength tunable filter)
11 Input waveguide (corresponding to input channel waveguide)
12 First slab waveguide (corresponding to slab waveguide on the input side)
13 Arrayed waveguide 14 Second slab waveguide (corresponding to slab waveguide on output side)
15 Output waveguide (corresponding to output channel waveguide)
20 groove 21 optical resin (corresponds to material)
30 Heater (corresponding to the mechanism for heating or cooling the material)
31 (External) heater 32 Thin film heater 40 Electrical wiring 60 First optical coupler (corresponding to directional coupler)
61 Second optical coupler (corresponding to directional coupler)
62 first arm waveguide 63 second arm waveguide 70 input / output waveguide 71 ring waveguide 72 directional coupler 80 ring resonator 121 first groove 122 second groove 131 first heater 132 second Heater 200 optical signal monitor 201 AWG (corresponding to wavelength tunable filter)
500 CSP type PD array 501 PD (corresponding to photodiode)
502 Housing 503 Glass window 700 Optical signal 701 Transmission characteristics of AWG 702 Monitor signal

Claims (8)

In an optical signal monitor that demultiplexes input wavelength multiplexed light and outputs a plurality of lights of different wavelengths,
A plurality of channel waveguides having different lengths, and a plurality of channel waveguides for demultiplexing the wavelength-multiplexed light by a change in wavelength of a phase difference generated between the plurality of channel waveguides;
A material that is arranged so as to intersect the traveling direction of light, and that changes the phase difference with respect to light of each wavelength according to temperature;
A mechanism for heating or cooling the material;
An optical signal monitor comprising one or a plurality of photodiodes arranged in an output unit. An arrayed waveguide grating composed of the plurality of channel waveguides having different lengths by a predetermined length;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed waveguide grating and a plurality of output channel waveguides;
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
The slab waveguide on the input side or the output side is between the paths from the input slab waveguide to the output slab waveguide through a plurality of channel waveguides for each wavelength of light input The material for changing the generated phase difference is filled in a groove formed in a curved shape so as to intersect the traveling direction of light,
The groove is formed by removing the upper cladding and the core from the input-side or output-side slab waveguide, or from the input-side or output-side slab waveguide, the upper cladding, the core, and the core Formed by removing the lower cladding,
The optical signal monitor according to claim 1, wherein the material is a material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of a slab waveguide including the material. The grooves are a plurality of grooves formed in the input-side or output-side slab waveguide for filling the material,
The plurality of grooves are grouped;
The optical signal monitor according to claim 2, further comprising a mechanism for heating or cooling the material independently for each group. An arrayed waveguide grating composed of the plurality of channel waveguides having different lengths by a predetermined length;
A slab waveguide on the input side disposed between the arrayed waveguide grating and the input channel waveguide;
An output-side slab waveguide disposed between the arrayed-waveguide diffraction grating and the output channel waveguide;
Each of the waveguides is composed of an upper clad, a core, and a lower clad,
A groove is formed across the arrayed waveguide grating,
The groove is formed by removing the upper cladding and the core from the channel waveguide, or formed by removing the upper cladding, the core, and the lower cladding from the channel waveguide,
The optical signal monitor according to claim 1, wherein the groove is filled with the material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of the channel waveguide. The groove is a plurality of grooves for filling the material formed across the plurality of channel waveguides constituting the arrayed waveguide diffraction grating,
The plurality of grooves are grouped;
The optical signal monitor according to claim 4, wherein a mechanism for independently heating or cooling the second material is provided for each group. The plurality of channel waveguides are:
It consists of an upper cladding, a core, and a lower cladding,
N sets of arm waveguides sandwiched between N + 1 (N is an integer of 1 or more) optical couplers and an adjacent optical coupler,
Each of the N sets of arm waveguides includes a first arm waveguide and a second arm waveguide having different optical path lengths,
A groove is formed in at least one of the first arm waveguide or the second arm waveguide;
The groove is formed by removing the upper clad and the core from an arm waveguide in which the groove is formed, or the upper clad, the core, and the core from an arm waveguide in which the groove is formed. Formed by removing the lower cladding,
The optical signal monitor according to claim 1, wherein the groove is filled with the material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of an arm waveguide in which the groove is formed. The plurality of channel waveguides are:
It consists of an upper cladding, a core, and a lower cladding,
Each output of the first optical branching coupler configured by connecting one or more optical branching couplers and having an output of M (M is an integer of 2 or more) ports, and one or more optical branching Each of which is provided between each input of a second optical branching coupler having a number of input ports equal to the number of ports of the first optical branching coupler configured by connecting the couplers. M delay waveguides having different delay amounts,
A groove is formed in a part of at least one of the M delay waveguides;
The groove is formed by removing the upper cladding and the core from the delay waveguide in which the groove is formed, or the upper cladding, the core, and the core from the delay waveguide in which the groove is formed. Formed by removing the lower cladding,
The optical signal monitor according to claim 1, wherein the groove is filled with the material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of the delay waveguide in which the groove is formed. . The plurality of channel waveguides are a circular ring waveguide and one or two input / output waveguides,
The ring waveguide is composed of an upper clad, a core, and a lower clad,
The ring waveguide has a groove formed by removing the upper clad and the core from the ring waveguide, or by removing the upper clad, the core, and the lower clad from the ring waveguide. Prepared,
2. The optical signal monitor according to claim 1, wherein the groove is filled with the material having a refractive index temperature coefficient different from a temperature coefficient of an effective refractive index of the ring waveguide.

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