Optical module and method for controlling optical module

Abstract

This optical module is provided with: a semiconductor laser (5); and an optical monitor (6) that receives the laser light from the semiconductor laser (5) and outputs a first monitoring value and a second monitoring value for estimating the intensity and wavelength of the laser light from the semiconductor laser (5). The optical monitor (6) constitutes an optical interferometer having: a first optical coupler (61a) that receives laser light from the semiconductor laser (5); a second optical coupler (61b) that receives laser light from the semiconductor laser (5); a first light receiver (65a) that outputs a first monitoring value; and a second light receiver (65b) that outputs a second monitoring value, and a first path from the first optical coupler (61a) to the first light receiver (65a) and a second path from the second optical coupler (61b) to the second light receiver (65b) are asymmetrical.

Description

Technical Field

[0001] This disclosure relates to optical modules and methods for controlling optical modules, and particularly to optical modules having a single-wavelength semiconductor laser and methods for controlling optical modules. Background Technology

[0002] As one of the methods for increasing the capacity of optical communication systems, digital coherent communication is employed. Digital coherent communication transmits signals across multiple channels, carrying signals not only in intensity but also in phase. Because optical interference is used to extract phase information, the wavelengths of the light source in the transmitter and the locally oscillating light acting as the interference light in the receiver must be precisely controlled.

[0003] These light sources are single-mode lasers.

[0004] Single-mode lasers oscillate with a single wavelength; however, the oscillation wavelength and light output intensity can vary due to manufacturing errors and ambient temperature.

[0005] Therefore, a wavelength lockout for wavelength control and a light intensity monitor are necessary in a light source module for digital coherent communication equipped with a single-mode laser.

[0006] Patent document 1 shows a laser module that locks the wavelength of a laser within a desired range.

[0007] The laser module shown in Patent Document 1 controls the temperature of the first Peltier element and the second Peltier element by comparing the monitoring output of the light receiving element that monitors the light emitted from the rear end face of the laser through the lens and beam splitter with the monitoring output of the light receiving element that monitors the light through the etalon, thereby locking the wavelength of the laser within the desired range.

[0008] The laser module shown in Patent Document 1 has a laser, a third condenser lens, a first condenser lens, a beam splitter, two light-receiving elements, and a thermistor mounted on the mounting surface of the first Peltier element, and a standard etalon mounted on the mounting surface of the second Peltier element.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2003-69130 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The laser module shown in Patent Document 1 has Peltier elements respectively placed in the laser and the etalon, and has a large number of components.

[0014] Furthermore, since a etalon is used, a component is needed to collimate the light incident on the etalon, and the size of the etalon itself also needs to be certain.

[0015] This disclosure was made in view of the above-mentioned aspects, and its purpose is to provide an optical module that emits a single wavelength with fewer components and can be miniaturized.

[0016] Methods for solving problems

[0017] The optical module disclosed herein includes: a semiconductor laser; and an optical monitor that receives laser light from the semiconductor laser and outputs a first monitoring value and a second monitoring value for estimating the intensity and wavelength of the laser light from the semiconductor laser. The optical monitor constitutes an optical interferometer having: a first optical coupler that receives laser light from the semiconductor laser; a second optical coupler that receives laser light from the semiconductor laser; a first photodetector that outputs the first monitoring value; and a second photodetector that outputs the second monitoring value. The first path from the first optical coupler to the first photodetector and the second path from the second optical coupler to the second photodetector are asymmetric.

[0018] Invention Effects

[0019] According to this disclosure, it is possible to precisely control a single wavelength, and the number of components is small, enabling miniaturization. Attached Figure Description

[0020] Figure 1 This is a perspective view showing the optical module in Embodiment 1 with the cover removed.

[0021] Figure 2 This is a perspective view showing the optical module of Embodiment 1.

[0022] Figure 3 yes Figure 1 Sectional view III-III.

[0023] Figure 4 This is a block diagram showing the optical monitor in the optical module of Embodiment 1.

[0024] Figure 5 This is a three-dimensional schematic diagram showing the optical monitor in the optical module of Embodiment 1.

[0025] Figure 6 This is a schematic block diagram showing the optical module device of Embodiment 1.

[0026] Figure 7 This is a diagram showing the output obtained from the optical monitor in the optical module device of Embodiment 1.

[0027] Figure 8This is a graph showing the sum of the first and second monitoring values ​​obtained by the optical monitor in the optical module device of Embodiment 1, namely the optical power monitoring value Ip, and the difference between the first and second monitoring values, namely the wavelength monitoring value Iλ.

[0028] Figure 9 This is a flowchart illustrating the operation of the optical module in Embodiment 1.

[0029] Figure 10 This diagram illustrates the state in which the backward laser beam of the semiconductor laser in the optical module of Embodiment 1 is offset relative to the first coupler and the second optical coupler.

[0030] Figure 11 This is a diagram showing the equiphase surface of the semiconductor laser in the optical module of Embodiment 1, where the backward laser beam of the semiconductor laser has a positional offset relative to the first coupler and the second optical coupler.

[0031] Figure 12 This is a diagram showing the results of estimating the mounting offset and coupling tilt in the optical module of Embodiment 1.

[0032] Figure 13 This is a three-dimensional schematic diagram showing the optical monitor in the optical module of Embodiment 2.

[0033] Figure 14 This is a diagram showing the output obtained by the optical monitor in the optical module of Embodiment 2.

[0034] Figure 15 This is a three-dimensional schematic diagram showing the optical monitor in the optical module of Embodiment 3.

[0035] Figure 16 This is a graph showing the waveforms of the I-type photocurrent, the Q-type photocurrent, the I-type photocurrent, and the relationship between the Q-type photocurrent and the optical power monitoring value Ip and the wavelength monitoring value Iλ in the optical module of Embodiment 3. Detailed Implementation

[0036] Implementation method 1.

[0037] according to Figures 1-12 This describes the optical module of Implementation Method 1.

[0038] The optical module in Implementation 1 is preferably used as a light source module for digital coherent communication.

[0039] The optical module in Implementation 1 is an example of a TO-CAN type optical transmission module used in optical communication.

[0040] The optical module in Implementation 1 is an optical module with a single-wavelength semiconductor laser.

[0041] The optical module of Implementation 1 is an optical module that has the functions of temperature regulation of semiconductor laser and monitoring of light output from semiconductor laser and monitoring of oscillation wavelength.

[0042] Therefore, the following explanation will take the TO-CAN type optical transmission module used for optical communication as an example.

[0043] like Figures 1-3 As shown, the optical module of Embodiment 1 includes a stem 1, a temperature regulator 2, a base 3, a secondary mounting component for a semiconductor laser (hereinafter referred to as the secondary mounting component) 4, a semiconductor laser 5, a planar waveguide type optical monitor (hereinafter referred to as the optical monitor) 6, a cover 7, multiple lead pins P1 to P6, and a grounding pin P7.

[0044] In addition, Figure 1 and Figure 3 To avoid complexity, the wires that connect the structural elements 2, 5, and 6 to pins P1 to P6 are omitted.

[0045] Support 1 is made of a circular plate of metal. Support 1 is not limited to a circular plate shape; it can also be cylindrical or quadrangular prism-shaped, as long as it is a flat plate with an inner plane 1a and an outer plane 1b parallel to the inner plane 1a.

[0046] The inner plane 1a of the support 1 is the mounting surface, which becomes the area for component mounting.

[0047] In this example, support 1 is a circular plate of metal with a diameter of 5.6 mm.

[0048] The support 1 and the cover 7 are combined to form package 10. Package 10 is a TO-CAN type package.

[0049] Cover 7 is a cover with windows that are open at one end and have a bottom and side walls.

[0050] The cover 7 is a metal lens cover made of cylindrical metal with an outer diameter slightly smaller than that of the support 1.

[0051] An opening is formed at the center of the bottom of the cover 7, and the opening is fitted with a flat glass or lens, which serves as a window 8.

[0052] The flat glass or lens of window 8 is joined and installed at the opening by adhesive or fusion, the opening being formed at the bottom in a manner that maintains airtightness both inside and outside the cover.

[0053] The end face of the side wall of the cover 7 is connected to the peripheral end of the inner plane 1a of the support 1 by electric welding and fixed.

[0054] The interior, surrounded by support 1 and cover 7, is filled with inert gas or becomes a vacuum, thus cutting off the semiconductor laser 5 from the external gas and sealing it in an airtight manner.

[0055] A forward laser Lf from semiconductor laser 5 is emitted from window 8.

[0056] The temperature regulator 2 is housed within the package 10 and mounted on the support 1.

[0057] The temperature regulator 2 has a lower surface 2a that is a flat surface and an upper surface 2b that is a flat surface parallel to the lower surface 2a. The lower surface 2a is fixed to the inner plane 1a of the support 1 by solder or conductive adhesive, and the upper surface 2b is the mounting surface. Hereinafter, the upper surface 2b will be referred to as the mounting surface.

[0058] Temperature regulator 2 heats or cools mounting surface 2b by passing photocurrent.

[0059] When the monitored value from the optical monitor 6 deviates from the set monitored value, the temperature regulator 2 controls the temperature supplied to the semiconductor laser 5 and the optical monitor 6 to change.

[0060] That is, the temperature regulator 2 regulates the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6.

[0061] Temperature regulator 2 is a thermoelectric cooler (TEC) composed of Peltier elements.

[0062] The base 3 is an L-shaped metal component placed on the mounting surface 2b of the temperature regulator 2, and has: a flat part 3a, the upper and lower surfaces of which are flat; and a vertical part 3b, which is integrally formed with the flat part 3a and has a flat vertical surface.

[0063] The lower surface of the flat portion 3a in the base 3 is fixed to the mounting surface 2b of the temperature regulator 2 by solder or conductive adhesive.

[0064] The semiconductor laser 5 is fixed on the facade 3b of the base 3 via a semiconductor laser mounting component 4.

[0065] The semiconductor laser 5 is fixed to the vertical surface of the vertical surface 3b in the base 3 in such a way that the optical axes of the forward laser Lf and the backward laser Lb of the semiconductor laser 5 are aligned with the central axis of the support 1.

[0066] Sub-mount 4 is, for example, made of a substrate, which is made of an aluminum nitride (AlN) dielectric with a pattern of metal wiring layers formed on its surface.

[0067] A fixed optical monitor 6 is mounted on the upper surface of the planar portion 3a in the base 3.

[0068] The optical monitor 6 is fixed to the upper surface of the planar portion 3a in the base 3 in order to receive the backward laser Lb from the semiconductor laser 5.

[0069] The optical monitor 6 is configured to receive the angle of the backward laser Lb from the semiconductor laser 5.

[0070] That is, the optical monitor 6 and the semiconductor laser 5 are configured to obtain the first optical coupler 61a and the second optical coupler 61b in the optical monitor 6 (refer to) the back laser Lb of the semiconductor laser 5. Figure 4 and Figure 5 The angle of maximum coupling efficiency.

[0071] For example, the backward laser Lb of the semiconductor laser 5 is configured to illuminate the first optical coupler 61a and the second optical coupler 61b in the optical monitor 6 at approximately perpendicular angles.

[0072] In this example, the base 3 is manufactured with the upper surface of the planar portion 3a and the surface of the vertical portion 3b, i.e., the mounting surface of the sub-mount 4, inclined. The angle formed by the upper surface of the planar portion 3a and the surface of the vertical portion 3b, i.e., the interior angle, is more than 90 degrees. The semiconductor laser 5 and the optical monitor 6 are arranged at an angle on the base 3.

[0073] In this way, by making the angle between the upper surface of the planar portion 3a and the surface of the vertical portion 3b, i.e. the interior angle, not completely perpendicular but deviating from 90 degrees, it is possible to suppress the reflected light of the back laser Lb of the semiconductor laser 5 reflected from the first optical coupler 61a and the second optical coupler 61b in the optical monitor 6 from being incident on the semiconductor laser 5.

[0074] As a result, unstable laser operation in semiconductor laser 5 can be avoided.

[0075] The base 3 conducts heat from the mounting surface 2b of the temperature regulator 2, and adjusts the temperature of the semiconductor laser 5 through the sub-mount 4, that is, heats or cools the semiconductor laser 5.

[0076] At the same time, the base 3 conducts heat from the mounting surface 2b of the temperature regulator 2 to regulate the temperature of the optical monitor 6, that is, to heat or cool the optical monitor 6.

[0077] The semiconductor laser 5 and the optical monitor 6, whose temperature is regulated by the temperature regulator 2, are arranged in the vertical direction via the base 3. Therefore, the dedicated area of ​​the semiconductor laser 5 and the optical monitor 6 at the mounting surface 2b of the temperature regulator 2 can be reduced. As a result, the temperature regulator 2 is miniaturized, and the optical module is miniaturized.

[0078] Semiconductor laser 5 is a single-wavelength semiconductor laser, which is a single-mode laser that oscillates at a so-called single wavelength. As a single-wavelength semiconductor laser, for example, a distributed feedback (DFB) laser diode element (chip) or a distributed bragg reflector (DBR) laser diode element (chip) is used.

[0079] Semiconductor laser 5 emits a forward laser Lf from the emission surface and a backward laser Lb from the rear surface. The forward laser Lf is used for optical communication, and the backward laser Lb is used for monitoring.

[0080] The light intensity of such a single-wavelength semiconductor laser varies depending on the supplied driving photocurrent, and also varies depending on the temperature of the semiconductor laser itself. Generally speaking, the lower the temperature, the greater the light output.

[0081] Furthermore, the oscillation wavelength of laser light from a single-wavelength semiconductor laser also varies depending on the temperature within the laser. The oscillation wavelength of laser light from a single-wavelength semiconductor laser also varies due to Joule heating caused by the driving photocurrent.

[0082] Therefore, in embodiment 1, the back laser Lb from the semiconductor laser 5 is monitored by the optical monitor 6, and the temperature of the semiconductor laser 5 is adjusted by the temperature regulator 2 to maintain the wavelength of the laser oscillating from the semiconductor laser 5 at a fixed value.

[0083] The optical monitor 6 outputs the monitored value to the control unit 9 that controls the temperature regulator 2 (see reference). Figure 6 This monitored value is used to enable the temperature regulator 2 to control the temperature supplied to the semiconductor laser 5 and the optical monitor 6 to change.

[0084] The control unit 9 controls the temperature regulator 2, the semiconductor laser 5, and the optical monitor 6. The control unit 9 exchanges signals with the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2 respectively, controls the photocurrent and voltage to the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2, and controls the light intensity and wavelength of the laser light from the semiconductor laser 5.

[0085] The optical monitor 6 measures the light intensity of the backward laser Lb from the semiconductor laser 5 and outputs a first monitoring value and a second monitoring value for estimating the intensity and wavelength of the forward laser Lf from the semiconductor laser 5.

[0086] The optical monitor 6 constitutes an optical interferometer, which includes: a first optical coupler 61a receiving a backward laser beam Lb from the semiconductor laser 5; a second optical coupler 61b receiving a backward laser beam Lb from the semiconductor laser 5; a first receiver 65a outputting a first monitoring value; and a second receiver 65b outputting a second monitoring value. The first path from the first optical coupler 61a to the first receiver 65a and the second path from the second optical coupler 61b to the second receiver 65b are asymmetrical. The optical interferometer is, for example, a Mach-Zehnder interferometer.

[0087] The sum of the first monitoring value and the second monitoring value becomes the optical power monitoring value Ip, which is composed of the photocurrent value used to control the value of the driving photocurrent to the semiconductor laser 5 in a manner that targets the light output of the semiconductor laser 5.

[0088] The difference between the first monitoring value and the second monitoring value is called the wavelength monitoring value Iλ, which is composed of the photocurrent value used to control the photocurrent supplied to the temperature regulator 2 in a manner that targets the wavelength of the laser from the semiconductor laser 5.

[0089] The optical monitor 6 is part of a wavelength lock for wavelength control of the laser light from the semiconductor laser 5.

[0090] The temperature regulator 2 performs the following control: when the optical power monitoring value Ip is greater than the photocurrent setting value, the mounting surface 2b is heated according to the value of the supplied photocurrent, so that the temperature supplied to the semiconductor laser 5 and the optical monitor 6 rises; when the optical power monitoring value Ip is less than the photocurrent setting value, the mounting surface 2b is cooled according to the value of the supplied photocurrent, so that the temperature supplied to the semiconductor laser 5 and the optical monitor 6 drops.

[0091] The photocurrent setting value is, for example, set to ±10% of the target value Ip_target of the optical power monitoring value Ip when the driving photocurrent of the semiconductor laser 5 is supplied to the semiconductor laser 5 with the optical output, i.e., the optical intensity, is the target value.

[0092] When the ratio of the optical power monitoring value Ip to the wavelength monitoring value Iλ, i.e., the wavelength monitoring value Iλ / Ip, deviates from the wavelength setting value, the temperature regulator 2 changes the temperature of the mounting surface 2b according to the value of the supplied photocurrent, thereby changing the temperature supplied to the semiconductor laser 5 and the optical monitor 6.

[0093] In this example, the temperature regulator 2 performs the following control: when the wavelength monitoring value Iλ / Ip is greater than the wavelength setting value, the mounting surface 2b is heated according to the value of the supplied photocurrent, so that the temperature supplied to the semiconductor laser 5 and the optical monitor 6 increases; when the wavelength monitoring value Iλ / Ip is less than the wavelength setting value, the mounting surface 2b is cooled according to the value of the supplied photocurrent, so that the temperature supplied to the semiconductor laser 5 and the optical monitor 6 decreases.

[0094] The wavelength setting value is, for example, set to ±10% of the target value Iλ_target of the wavelength monitoring value Iλ / Ip when the wavelength λLD of the laser of the semiconductor laser 5 is set to the target value λ_target.

[0095] like Figure 4 and Figure 5 As shown, the optical monitor 6 has a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical multiplexer / demultiplexer 64, a first light receiver 65a, a second light receiver 65b, and a phase adjuster 66.

[0096] The output-side optical combiner / splitter 64, the first optical receiver 65a, and the second optical receiver 65b function as an interferometric measurement system for observing wavelength dependence.

[0097] The output-side optical combiner / splitter 64 is an optical circuit of the interferometric measurement system composed of the first optical receiver 65a and the second optical receiver 65b.

[0098] The optical monitor 6 is, for example, a planar waveguide-type optical monitor based on a silicon photonic chip, which is formed by integrating a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical multiplexer / demultiplexer 64, a first photodetector 65a, and a second photodetector 65b on a plane of a silicon (Si) substrate 6A.

[0099] Phase modulator 66 is located on a portion of the second asymmetric arm 63b and is formed on an insulating film (not shown) formed on the surface of the silicon photonic chip.

[0100] The first optical coupler 61a receives the backward laser Lb from the semiconductor laser 5, and couples the backward laser Lb, which is perpendicularly incident on the plane 6a of the optical monitor 6, to the first optical waveguide 62a that constitutes the input-side optical multiplexer / demultiplexer 62.

[0101] The second optical coupler 61b receives the backward laser Lb from the semiconductor laser 5, and couples the backward laser Lb, which is perpendicularly incident on the plane 6a of the optical monitor 6, to the second optical waveguide 62b that constitutes the input-side optical multiplexer / demultiplexer 62.

[0102] The first optical coupler 61a and the second optical coupler 61b are, for example, grating couplers. The grating coupler has the function of coupling the backward laser Lb from the semiconductor laser 5, which is emitted from above the plane 6a of the optical monitor 6, to the first optical waveguide 62a and the second optical waveguide 62b that constitute the input-side optical multiplexer / demultiplexer 62, respectively. Therefore, the plane 6a of the optical monitor 6 and the semiconductor laser 5 are configured by the base 3 at an angle that can achieve the maximum coupling efficiency of the grating coupler.

[0103] Alternatively, the optical coupler 61 can also be an electronic coupler.

[0104] Grating couplers can amplify the light pattern, and therefore have the characteristic of being less position-dependent than waveguide end-face coupling. Therefore, in this example, the first optical coupler 61a and the second optical coupler 61b are preferably grating couplers.

[0105] The input-side optical wave combiner / demultiplexer 62 is a 2×2 optical wave combiner / demultiplexer with ports 1 to 4, a first optical waveguide 62a connecting ports 1 and 2, and a second optical waveguide 62b connecting ports 3 and 4.

[0106] In the input-side optical multiplexer / demultiplexer 62, port 1 is coupled to the first optical coupler 61a, and port 3 is coupled to the second optical coupler 61b.

[0107] The input-side optical multiplexer / demultiplexer 62 is an asymmetric optical multiplexer / demultiplexer; in this example, the power split ratio is set to 0.8, for example. In other words, the power split ratio relative to the first optical waveguide 62a and the second optical waveguide 62b is set to 2:8.

[0108] In addition, an asymmetric optical combiner / demultiplexer refers to an optical combiner / demultiplexer with a power split ratio that varies from 0.5 onwards.

[0109] In the optical module of Embodiment 1, one feature is that an asymmetric optical multiplexer / demultiplexer is used as the input-side optical multiplexer / demultiplexer 62.

[0110] In the case where the optical monitor 6 is configured as a planar waveguide type optical monitor based on a silicon photonic chip, the first optical waveguide 62a and the second optical waveguide 62b constituting the input-side optical multiplexer / demultiplexer 62 are silicon waveguides formed of silicon.

[0111] The length of the first optical waveguide 62a is the same as the length of the second optical waveguide 62b.

[0112] It is possible to use any one of the following, such as a directional coupler and a multi-mode interferometer (MMI), having ports 1 to 4 and having a light propagation path from port 1 to port 2 and a light propagation path from port 3 to port 4, as an input-side optical multiplexer / demultiplexer 62.

[0113] In this example, the propagation path of light from port 1 to port 2 is referred to as the first optical waveguide 62a, and the propagation path of light from port 3 to port 4 is referred to as the second optical waveguide 62b.

[0114] The input node of the first asymmetric arm 63a is optically connected to the second port of the input-side optical multiplexer / demultiplexer 62.

[0115] In the case where the optical monitor 6 is composed of a planar waveguide-type optical monitor based on a silicon photonic chip, the first asymmetric arm 63a is a silicon waveguide formed of silicon.

[0116] Furthermore, the second port of the input-side optical multiplexer / demultiplexer 62 and the input node of the first asymmetric arm 63a are not physically separated, but are continuously formed as the connection point of the silicon waveguides constituting the first optical waveguide 62a and the first asymmetric arm 63a of the input-side optical multiplexer / demultiplexer 62.

[0117] The input node of the second asymmetric arm 63b is optically connected to the fourth port of the input-side optical multiplexer / demultiplexer 62.

[0118] In the case where the optical monitor 6 is composed of a planar waveguide-type optical monitor based on a silicon photonic chip, the second asymmetric arm 63b is a silicon waveguide formed of silicon.

[0119] Furthermore, the fourth port of the input-side optical multiplexer / demultiplexer 62 and the input node of the second asymmetric arm 63b are not physically separated, but are continuously formed as the connection point of the silicon waveguides constituting the first optical waveguide 62a and the second asymmetric arm 63b of the input-side optical multiplexer / demultiplexer 62.

[0120] The length of the optical waveguide in the first asymmetric arm 63a is ΔL longer than the length of the optical waveguide in the second asymmetric arm 63b.

[0121] Since the length of the optical waveguide in the first asymmetric arm 63a is different from the length of the optical waveguide in the second asymmetric arm 63b, the light propagating in the first asymmetric arm 63a and the light propagating in the second asymmetric arm 63b are obtained by shifting the phase according to the anti-phase relation.

[0122] The output-side optical wave combiner / demultiplexer 64 is a 2×2 optical wave combiner / demultiplexer with ports 1 to 4, a third optical waveguide 64a connecting ports 1 and 2, and a fourth optical waveguide 64b connecting ports 3 and 4.

[0123] In the output-side optical combiner / splitter 64, port 1 is the first input node for forming the optical loop of the interferometric measurement system, port 2 is the first output node for forming the optical loop of the interferometric measurement system, port 3 is the second input node for forming the optical loop of the interferometric measurement system, and port 4 is the second output node for forming the optical loop of the interferometric measurement system.

[0124] In the output-side optical multiplexer / demultiplexer 64, the first port is optically connected to the output node of the first asymmetric arm 63a, and the third port is optically connected to the output node of the second asymmetric arm 63b.

[0125] The output-side optical multiplexer / demultiplexer 64 is an asymmetric optical multiplexer / demultiplexer; in this example, for instance, the power split ratio is set to 0.8. In other words, the power split ratio relative to the third optical waveguide 64a and the fourth optical waveguide 64b is set to 2:8.

[0126] In addition, an asymmetric optical combiner / demultiplexer refers to an optical combiner / demultiplexer with a power split ratio that varies from 0.5 onwards.

[0127] In the optical module of embodiment 1, one of the features is that an asymmetric optical multiplexer / demultiplexer is used as the output-side optical multiplexer / demultiplexer 64.

[0128] The third optical waveguide 64a and the fourth optical waveguide 64b constituting the output-side optical multiplexer / demultiplexer 64 are silicon waveguides formed of silicon when the optical monitor 6 is composed of a planar waveguide type optical monitor based on a silicon photonic chip.

[0129] The length of the third optical waveguide 64a is the same as the length of the fourth optical waveguide 64b.

[0130] Furthermore, the first port of the output-side optical multiplexer / demultiplexer 64 and the output node of the first asymmetric arm 63a are not physically separated, but are continuously formed as the connection point of the silicon waveguides constituting the third optical waveguide 64a and the first asymmetric arm 63a of the output-side optical multiplexer / demultiplexer 64.

[0131] Furthermore, the third port and the output node of the second asymmetric arm 63b of the output-side optical multiplexer / demultiplexer 64 are not physically separated, but are continuously connected to form the connection point of the silicon waveguides of the fourth optical waveguide 64b and the second asymmetric arm 63b of the output-side optical multiplexer / demultiplexer 64.

[0132] It is possible to use any one of, such as a directional coupler and an MMI waveguide, having ports 1 to 4 and optical propagation paths from port 1 to port 2 and from port 3 to port 4, as an output-side optical multiplexer / demultiplexer 64.

[0133] In this example, the propagation path of light from port 1 to port 2 is referred to as the third optical waveguide 64a, and the propagation path of light from port 3 to port 4 is referred to as the fourth optical waveguide 64b.

[0134] The input-side optical combiner / demultiplexer 62, the first asymmetric arm 63a, the second asymmetric arm 63b, and the output-side optical combiner / demultiplexer 64 constitute a so-called optical interferometer.

[0135] The first photodetector 65a receives light from the second port of the output-side optical multiplexer / demultiplexer 64 and performs photoelectric conversion, outputting a first monitoring value composed of photocurrent.

[0136] The first photodetector 65a is a waveguide-type photodetector or a surface-incident photodetector. In this example, a photodiode is used as a SiGe (silicon germanium) photodetector.

[0137] The second photodetector 65b receives light from the fourth port of the output-side optical multiplexer / demultiplexer 64 and performs photoelectric conversion, outputting a second monitoring value composed of photocurrent.

[0138] The second photodetector 65b is a waveguide-type photodetector or a surface-incident photodetector. In this example, a photodiode is used as a SiGe photodetector.

[0139] In the case where the optical monitor 6 is configured as a planar waveguide-type optical monitor based on a silicon photonic chip, the first path is the propagation path of light based on the silicon waveguide from the first port of the input-side optical multiplexer / demultiplexer 62, through the input-side optical multiplexer / demultiplexer 62, the first asymmetric arm 63a, and the output-side optical multiplexer / demultiplexer 64 to the second port of the output-side optical multiplexer / demultiplexer 64.

[0140] The second path is a silicon waveguide-based light propagation path from the third port of the input-side optical multiplexer / demultiplexer 62, through the input-side optical multiplexer / demultiplexer 62, the second asymmetric arm 63b, and the output-side optical multiplexer / demultiplexer 64 to the fourth port of the output-side optical multiplexer / demultiplexer 64.

[0141] The backward laser Lb from the semiconductor laser 5 received by the first optical coupler 61a and the backward laser Lb from the semiconductor laser 5 received by the second optical coupler 61b are split and interfered by the input-side optical multiplexer / demultiplexer 62, respectively, and propagate from the second port of the input-side optical multiplexer / demultiplexer 62 to the first asymmetric arm 63a, and from the fourth port of the input-side optical multiplexer / demultiplexer 62 to the second asymmetric arm 63b.

[0142] The laser propagating in the first asymmetric arm 63a and the laser propagating in the second asymmetric arm 63b are split and interfered by the output-side optical combiner / demultiplexer 64, respectively, and propagate from the second port of the output-side optical combiner / demultiplexer 64 to the first photodetector 65a, and from the fourth port of the output-side optical combiner / demultiplexer 64 to the second photodetector 65b.

[0143] The backward laser Lb received by the first optical coupler 61a from the semiconductor laser 5 is incident on both the first photodetector 65a and the second photodetector 65b according to the respective power branch ratios of the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64, although the ratios vary depending on the wavelength.

[0144] Similarly, the backward laser Lb received by the second optical coupler 61b from the semiconductor laser 5 is incident on both the first photodetector 65a and the second photodetector 65b according to the respective power branch ratios of the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64, although the ratios vary depending on the wavelength.

[0145] In summary, the backward laser Lb from the semiconductor laser 5 received by the first optical coupler 61a and the backward laser Lb from the semiconductor laser 5 received by the second optical coupler 61b are split and interfered by the input-side optical multiplexer / splitter 62 and the output-side optical multiplexer / splitter 64, respectively, and propagate to the first photodetector 65a and the second photodetector 65b according to the ratio determined by the input-side optical multiplexer / splitter 62 and the output-side optical multiplexer / splitter 64 based on the wavelength.

[0146] Since the back laser Lb from the semiconductor laser 5 received by the first optical coupler 61a and the back laser Lb from the semiconductor laser 5 received by the second optical coupler 61b are incident on the input-side optical combiner / splitter 62 and the output-side optical combiner / splitter 64 without being reflected, the combined output of the input-side optical combiner / splitter 62 and the output-side optical combiner / splitter 64 can be regarded as the power obtained by coupling the back laser Lb from the semiconductor laser 5 received by the first optical coupler 61a and the back laser Lb from the semiconductor laser 5 received by the second optical coupler 61b.

[0147] The first photodetector 65a receives laser light from the second port of the output-side optical combiner / demultiplexer 64 and outputs the photocurrent after photoelectric conversion as the first monitoring value.

[0148] The second photodetector 65b receives the laser Lb from the second port of the output-side optical combiner / demultiplexer 64 and outputs the photocurrent after photoelectric conversion as the second monitoring value.

[0149] The backward laser Lb received by the first optical coupler 61a from the semiconductor laser 5 and the backward laser received by the second optical coupler 61b from the semiconductor laser 5 are interfered by the input-side optical combiner / decomposer 62 and the output-side optical combiner / decomposer 64 constituting the interferometer. Therefore, the photocurrent obtained by the first photodetector 65a has wavelength dependence.

[0150] Therefore, the first and second monitoring values ​​are also wavelength dependent.

[0151] When the length (physical length) of the light propagation path in the first asymmetric arm 63a is set as L1, and the length (physical length) of the light propagation path in the second asymmetric arm 63b is set as L2, the relationship between L1 and L2 is expressed by the following formula (1).

[0152] L1=L2+ΔL (1)

[0153] ΔL is the difference between the length of the optical waveguide in the first asymmetric arm 63a and the length of the optical waveguide in the second asymmetric arm 63b.

[0154] Furthermore, the phase θ after interference in the optical monitor 6, i.e. the phase difference θ between the first monitoring value and the second monitoring value in the optical monitor 6, can be represented by the following equation (2).

[0155]

[0156] n0 is the group refractive index of the first asymmetric arm 63a and the second asymmetric arm 63b, λ is the wavelength of the backward laser Lb, and m is a coefficient relating wavelength λ and optical path length nL, which is a variable proportional to phase θ.

[0157] The phase difference θ changes with temperature, and the group refractive index n0, the length L1 of the light propagation path in the first asymmetric arm 63a and the length L2 of the light propagation path in the second asymmetric arm 63b are determined in such a way that the temperature derivative of the above equation (2) is always 0. Thus, it is possible to obtain a light monitor 6 whose first and second monitoring values ​​are not temperature dependent.

[0158] The waveform obtained from the first monitored value from the first photodetector 65a is used as an example. Figure 7Waveform A is shown in the figure. The waveform obtained from the second monitoring value from the second photodetector 65b is used as an example. Figure 7 Waveform B is shown in the middle.

[0159] Figure 7 The waveform shown is with ΔL = 2,000 μm, electric field transmittance t = 0.9, and T = 0.9. si =T LD Examples are shown below, illustrating the photocurrent values ​​obtained by the first photodetector 65a and the second photodetector 65b, respectively.

[0160] exist Figure 7 In the diagram, the horizontal axis represents the wavelength of the backward laser Lb, and the vertical axis represents the intensity of the monitored value.

[0161] according to Figure 7 It can be seen that waveform A obtained from the first monitoring value and waveform B obtained from the second monitoring value are inversely related, i.e., inverted waveforms, with a phase shift of 180 degrees.

[0162] Therefore, in the control unit 9, if the first monitoring value based on photocurrent from the first photodetector 65a and the second monitoring value based on photocurrent from the second photodetector 65b are simply summed, the optical power monitoring value Ip, which is the sum of the first monitoring value and the second monitoring value, can be calculated.

[0163] That is, the sum of the photocurrent from the first photodetector 65a, which becomes the first monitoring value from the first photodetector 65a, and the photocurrent from the second photodetector 65b, which becomes the second monitoring value from the second photodetector 65b, is proportional to the sum of the power of the backward laser Lb from the semiconductor laser 5 received by the first optical coupler 61a and the backward laser Lb from the semiconductor laser 5 received by the second optical coupler 61b. Therefore, the sum of the first monitoring value and the second monitoring value can be used as the optical power monitoring value Ip.

[0164] The obtained optical power monitoring value Ip is twice the optical power value relative to the case of using one optical coupler and one optical receiver.

[0165] The waveform obtained by combining the first and second monitoring values ​​is used as an example. Figure 8 The waveform shown is C.

[0166] Figure 8 The waveform C shown is with ΔL = 2,000 μm, electric field transmission coefficient t = 0.9, and T = 0.9. si =T LD In the case of a photocurrent, the value is obtained by simply adding the photocurrent value obtained by the first photodetector 65a and the photocurrent value obtained by the second photodetector 65b.

[0167] exist Figure 8In the diagram, the horizontal axis represents the wavelength of the backward laser Lb, and the vertical axis represents the intensity.

[0168] Furthermore, since the photocurrent from the first photodetector 65a and the photocurrent from the second photodetector 65b are wavelength-dependent, the difference between the first monitoring value and the second monitoring value can be used as the wavelength monitoring value Iλ.

[0169] The waveform obtained by the difference between the first and second monitoring values ​​is used as an example. Figure 8 The waveform shown in the middle is D.

[0170] Figure 8 The waveform D shown is with ΔL of 2,000 μm, electric field transmission coefficient t of 0.9, and T... si =T LD In the example, the value is obtained by simply subtracting the photocurrent value obtained from the first photocurrent receiver 65a from the photocurrent value obtained from the second photocurrent receiver 65b.

[0171] By obtaining the difference between the first and second monitoring values, even using only one optical coupler and one photodetector, it is possible to obtain the slope of the photocurrent intensity that is twice the slope of the intensity of the photocurrent flowing in the photodetector.

[0172] The wavelength, measured by the monitoring value Iλ, varies not only according to the wavelength of the backward laser Lb from the semiconductor laser 5, but also according to the light intensity of the backward laser Lb.

[0173] Therefore, by dividing the wavelength by the monitoring value Iλ and the optical power monitoring value Ip, the wavelength monitoring value Iλ / Ip based solely on the wavelength of the backward laser Lb can be obtained.

[0174] The sensitivity of the first photodetector 65a and the second photodetector 65b changes due to temperature variations. However, by dividing the wavelength by the monitoring value Iλ and normalizing the wavelength monitoring value using the optical power monitoring value Ip, a high-precision wavelength monitoring value can be obtained.

[0175] In the optical module of Embodiment 1, the optical monitor 6 constitutes an optical interferometer, which has a first optical coupler 61a and a second optical coupler 61b. The first path from the first optical coupler 61a to the first photodetector 65a and the second path from the second optical coupler 61b to the second photodetector 65b are asymmetrical. A first monitoring value is obtained from the first photodetector 65a and a second monitoring value is obtained from the second photodetector 65b, resulting in an optical power monitoring value Ip and a wavelength monitoring value Iλ / Ip.

[0176] Therefore, compared to the case where the backward laser Lb from the semiconductor laser 5 is received by a single optical coupler and the optical power monitoring value Ip and the wavelength monitoring value Iλ / Ip are obtained by branching the backward laser Lb received by the optical coupler by 1 / 2 each time, in the optical module of Embodiment 1, the light-receiving area of ​​the backward laser Lb is doubled relative to a single optical coupler due to the first optical coupler 61a and the second optical coupler 61b.

[0177] Furthermore, since the wavelength monitoring value Iλ is obtained from the difference between the first monitoring value and the second monitoring value, although one optical coupler and one photodetector are used, the wavelength monitoring value Iλ is obtained by using a slope that is twice the slope of the intensity of the photocurrent flowing in the photodetector.

[0178] Therefore, compared to using a hypothetical single optical coupler, four times the back laser Lb from the semiconductor laser 5 can be used to obtain the optical power monitoring value Ip and the wavelength monitoring value Iλ / Ip.

[0179] As a result, an optical monitor 6 with a sensitivity four times that of the backlight laser Lb from the semiconductor laser 5 can be obtained, and a high-precision optical power monitoring value Ip and wavelength monitoring value Iλ / Ip can be obtained.

[0180] By adjusting the temperature in the semiconductor laser 5, the wavelength of the forward laser Lf in the semiconductor laser 5 can be adjusted.

[0181] The semiconductor laser 5 and the optical monitor 6 are temperature regulated by heat from the mounting surface 2b of the temperature regulator 2 via the base 3. Therefore, the temperature rise in the semiconductor laser 5 is the same as the temperature rise in the optical monitor 6.

[0182] The wavelength monitoring value Iλ / Ip has a downward slope to the right relative to the temperature rise in the optical monitor 6.

[0183] By knowing the wavelength monitoring value Iλ / Ip, the wavelength shift in the laser beam of semiconductor laser 5 can be determined.

[0184] When the forward laser Lf from semiconductor laser 5 is offset relative to the target wavelength (hereinafter referred to as target value λ_target) of the forward laser Lf from semiconductor laser 5, the wavelength monitoring value Iλ / Ip is also offset.

[0185] Therefore, the value of the photocurrent supplied to the temperature regulator 2 is controlled in such a way that the wavelength monitoring value Iλ / Ip does not deviate from the wavelength setting value (±10% of the target value Iλ_target), thereby adjusting the temperature in the semiconductor laser 5 and the temperature in the optical monitor 6.

[0186] As a result, it is possible to precisely control a single wavelength of the laser from the semiconductor laser 5.

[0187] In this example, the optical monitor 6 further configures the phase adjuster 66 on the second asymmetric arm 63b.

[0188] The phase adjuster 66 sets the phase state of the photocurrent output from the optical monitor 6 at the position where the wavelength dependence of the photocurrent at the target wavelength (hereinafter referred to as the target value λ_target) of the forward laser Lf from the semiconductor laser 5 reaches its maximum.

[0189] Phase adjuster 66 is, for example, a heater.

[0190] By flowing photocurrent in the heater that becomes phase adjuster 66 in a way that makes the target value Iλ_target a wavelength monitoring value Iλ / Ip suitable for control, the second path of optical monitor 6 (the second asymmetric arm 63b in this example) is heated, thereby regulating the temperature in the second asymmetric arm 63b.

[0191] The phase adjuster 66 adjusts the temperature in the second path of the optical monitor 6 in such a way that the wavelength-dependent slope is near the central value of the wavelength monitoring value Iλ / Ip in the region where the temperature change of the optical monitor 6 is large, and determines the target value Iλ_target.

[0192] Alternatively, the temperature in the first path (e.g., the first asymmetric arm 63a) of the optical monitor 6 can also be adjusted by the phase adjuster 66.

[0193] The phase modulator 66 can change the phase state of the photocurrent output from the optical monitor 6. It is not limited to a heater. It can also be a pin-type photocurrent injection refractive index modulator or a photocurrent extraction refractive index modulator, or a phase changer based on the photocurrent injection or extraction of the pn junction, or based on the quantum confinement Stark effect, the Pockels effect, etc., applied by voltage.

[0194] Alternatively, the optical monitor 6 can also be a planar waveguide type optical monitor obtained by integrating a first optical coupler 61a, a second optical coupler 61b, an input-side optical combiner / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical combiner / demultiplexer 64, a first light receiver 65a, and a second light receiver 65b on a plane of an indium phosphide (InP) substrate 6A, which is a compound semiconductor.

[0195] The optical monitor 6 can also be a planar waveguide type optical monitor obtained by integrating a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical multiplexer / demultiplexer 64, a first light receiver 65a, and a second light receiver 65b on the plane of the glass substrate 6A.

[0196] Furthermore, the first optical coupler 61a, the second optical coupler 61b, the input-side optical multiplexer / demultiplexer 62, the first asymmetric arm 63a, the second asymmetric arm 63b, the output-side optical multiplexer / demultiplexer 64, the first optical receiver 65a, and the second optical receiver 65b do not necessarily have to be integrated, or the individual structural elements can be modularized.

[0197] The first photodetector 65a and the second photodetector 65b can be InP-based photodetectors or GaAs-based photodetectors, respectively.

[0198] like Figure 6 As shown, the temperature regulator 2, the semiconductor laser 5, and the optical monitor 6 are controlled by the control unit 9.

[0199] The control unit 9 exchanges signals with the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2 respectively, controls the photocurrent and voltage to the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2 respectively, and controls the light intensity and wavelength of the laser from the semiconductor laser 5.

[0200] The control unit 9 receives the photocurrent from the first photodetector 65a (i.e., the first monitoring value) and the photocurrent from the second photodetector 65b (i.e., the second monitoring value), calculates the sum of the first and second monitoring values ​​(i.e., the optical power monitoring value Ip), the difference between the first and second monitoring values ​​(i.e., the wavelength monitoring value Iλ), and the ratio of the optical power monitoring value Ip to the wavelength monitoring value Iλ (i.e., the wavelength monitoring value Iλ / Ip).

[0201] In this example, the optical power monitoring value Ip is the value obtained by adding the first monitoring value obtained from the first photodetector 65a and the second monitoring value obtained from the second photodetector 65b (see reference). Figure 4 (Line C).

[0202] In this example, the wavelength monitoring value Iλ is obtained by subtracting the first monitoring value obtained from the first photodetector 65a from the second monitoring value obtained from the second photodetector 65b (see reference). Figure 4 Waveform curve D).

[0203] The control unit 9 controls the driving photocurrent supplied to the semiconductor laser 5 in such a way that the calculated optical power monitoring value Ip converges to within ±10% of the target value Ip_target of the optical power monitoring value, which is the photocurrent setting value.

[0204] The control unit 9 controls the photocurrent supplied to the temperature regulator 2 in such a way that the calculated optical power monitoring value Ip converges to the range of the photocurrent setting value of ±10% of the target value Ip_target of the optical power monitoring value.

[0205] When the optical power monitoring value Ip is greater than the photocurrent setting value, the control unit 9 supplies photocurrent for heating the mounting surface 2b of the temperature regulator 2 to the temperature regulator 2; when the optical power monitoring value Ip is less than the photocurrent setting value, the control unit 9 supplies photocurrent for cooling the mounting surface 2b of the temperature regulator 2 to the temperature regulator 2.

[0206] As a result, the temperature regulator 2 controls the temperature supplied to the semiconductor laser 5 and the optical monitor 6 to rise when the optical power monitoring value Ip is greater than the photocurrent setting value, and to decrease the temperature supplied to the semiconductor laser 5 and the optical monitor 6 when the optical power monitoring value Ip is less than the photocurrent setting value.

[0207] Furthermore, the control unit 9 controls the photocurrent supplied to the temperature regulator 2 in such a way that the calculated wavelength monitoring value Iλ / Ip converges to a wavelength setting value within ±10% of the target value Iλ_target of the wavelength monitoring value Iλ / Ip when the wavelength λLD of the laser of the semiconductor laser 5 is set to the target value λ_target.

[0208] When the wavelength monitoring value Iλ / Ip deviates from the wavelength setting value, the control unit 9 supplies photocurrent to the temperature regulator 2 to change the temperature of the mounting surface 2b.

[0209] In this example, when the wavelength monitoring value Iλ / Ip is greater than the wavelength setting value, the control unit 9 supplies photocurrent for heating the mounting surface 2b of the temperature regulator 2 to the temperature regulator 2; when the wavelength monitoring value Iλ / Ip is less than the wavelength setting value, the control unit 9 supplies photocurrent for cooling the mounting surface 2b of the temperature regulator 2 to the temperature regulator 2.

[0210] As a result, the temperature regulator 2 controls the temperature supplied to the semiconductor laser 5 and the optical monitor 6 to rise when the wavelength monitoring value Iλ / Ip is greater than the wavelength setting value, and to decrease the temperature supplied to the semiconductor laser 5 and the optical monitor 6 when the wavelength monitoring value Iλ / Ip is less than the wavelength setting value.

[0211] In addition, the temperature regulator 2 performs the following control: when the wavelength monitoring value Iλ / Ip is greater than the wavelength setting value, the temperature supplied to the semiconductor laser 5 and the optical monitor 6 is increased; when the optical power monitoring value Ip is less than the photocurrent setting value, the driving photocurrent supplied to the semiconductor laser 5 is increased; when the wavelength monitoring value Iλ / Ip is less than the wavelength setting value, the temperature supplied to the semiconductor laser 5 and the optical monitor 6 is decreased; when the optical power monitoring value Ip is greater than the photocurrent setting value, the driving photocurrent supplied to the semiconductor laser 5 is decreased.

[0212] The control unit 9 supplies the photocurrent with the target value Ih_target when the light intensity of the laser from the semiconductor laser 5 is the target value and the wavelength λLD of the laser from the semiconductor laser 5 is the target value λ_target to the phase modulator 66.

[0213] As a result, the heater, which acts as the phase adjuster 66, heats the optical monitor 6 under the control of the control unit 9, specifically, adjusting the temperature in the second path of the optical monitor 6 (the second asymmetric arm 63b in this example).

[0214] The control unit 9 and the optical monitor 6 constitute a wavelength lock for wavelength control of the laser light from the semiconductor laser 5.

[0215] The optical module device consists of an optical module and a control unit 9.

[0216] Since the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2 exchange signals with the control unit 9, they are electrically connected to pins P1 to P6 using gold wires or other leads (not shown) based on bonding wires.

[0217] Pins P1 to P6 pass through the through holes of support 1, and are fixed to support 1 by sealing glass obtained by filling the space between pins P1 to P6 and the through holes and allowing it to solidify. The sealing glass electrically insulates pins P1 to P6 from support 1 and maintains airtightness.

[0218] The internal lead connections of the pins P1 to P6 exposed from the inner plane of the support 1 are shown as an example. However, the relationship between pins P1 to P6 and the various structural elements is only shown as an example and is not limited thereto.

[0219] Pin P1 is connected to one electrode of the semiconductor laser 5, transmitting the drive photocurrent from the control unit 9 to the semiconductor laser 5. Pin P1 is the main signal pin for the semiconductor laser 5.

[0220] Pin P2 is connected to the first photodetector 65a of the optical monitor 6, and transmits the photocurrent representing the first monitoring value from the first photodetector 65a to the control unit 9. Pin P2 is the first monitoring pin relative to the optical monitor 6.

[0221] Pin P3 is connected to the second photodetector 65b of the optical monitor 6, and transmits the photocurrent representing the second monitoring value from the second photodetector 65b to the control unit 9. Pin P3 is the second monitoring pin relative to the optical monitor 6.

[0222] Pins P4 and P5 are connected to a pair of electrodes in the temperature regulator 2, and transmit the photocurrent supplied from the control unit 9 to the temperature regulator 2. Pins P4 and P5 are a pair of temperature control pins relative to the temperature regulator 2.

[0223] Pin P6 is connected to phase adjuster 66 and transmits the photocurrent supplied from control unit 9 to phase adjuster 66. Pin P6 is a phase adjustment pin relative to phase adjuster 66.

[0224] One end face of the grounding pin P7 is connected to the outer plane 1b of the support 1 by electric welding or brazing, and the grounding pin P7 is fixed to the support 1.

[0225] The grounding pin P7 is electrically connected, and the support 1 becomes grounded through the grounding pin P7. That is, the support 1 also serves as a grounding node.

[0226] The optical module in Implementation 1 can have a total of 7 pins, including 6 signal pins P1 to P6 and 1 ground pin P7 for each structural element, and can be constructed with a relatively small number of pins.

[0227] As a result, miniaturization can be achieved using a standard CAN package with a diameter of 5.6mm and a maximum of 7 pins.

[0228] Next, the operation of the optical module in Embodiment 1 will be explained.

[0229] Regarding optical modules, taking an optical module equipped with a semiconductor laser 5 as an example, the semiconductor laser 5 is a laser chip that has been confirmed to produce light output above the target within the operating temperature range and to obtain the target's oscillation wavelength within a controllable temperature range.

[0230] First, as a preparation for activating the optical module, the following steps are taken.

[0231] When the semiconductor laser 5 obtains light output with wavelength λLD as the target value λ_target and light intensity as the target value Ip_target of the optical power monitoring value Ip, the target value of the driving photocurrent supplied to the semiconductor laser 5, the target value of the photocurrent supplied to the temperature regulator 2, the target value of the photocurrent supplied to the phase regulator 66, and the target value of the photocurrent supplied to the phase regulator 66 are obtained.

[0232] These target values ​​are obtained using commonly known light intensity and wavelength measuring instruments.

[0233] Furthermore, the target value Ip_target of the optical power monitoring value Ip obtained from the semiconductor laser 5 at the same timing is the optical power monitoring value Ip with the target intensity as the target value, the target value Ip_target of the optical power monitoring value Ip when the optical output with wavelength λLD is the target value λ_target is obtained, the target value Iλ_target of the wavelength monitoring value Iλ / Ip when the wavelength λLD is set to the target value λ_target, and the wavelength dependence of the wavelength monitoring value Iλ / Ip near the target value Iλ_target.

[0234] In semiconductor laser 5, the photocurrent value ILD driving the photocurrent is proportional to the optical power monitoring value Ip, and the lower the temperature in semiconductor laser 5, the greater the light output, that is, the greater the optical power monitoring value Ip.

[0235] In this example, the driving photocurrent with the target value ILD_target is supplied to the semiconductor laser 5, and the temperature of the semiconductor laser 5 with the target value Ip_target and the wavelength λLD of the optical power monitoring value Ip is 55°C.

[0236] Furthermore, the target value Iλ_target of the wavelength monitoring value Iλ / Ip is set to be near the central value of the wavelength monitoring value Iλ / Ip when the temperature at semiconductor laser 5 and the temperature at optical monitor 6 change, and in the region where the slope of the wavelength dependence is large.

[0237] Next, the main use Figure 9 The operation of the optical module is explained.

[0238] When the optical module is started, the control unit 9 supplies the photocurrent of the target value Ih_target to the phase modulator 66 (step ST1).

[0239] Next, the control unit 9 supplies the driving photocurrent of the target value ILD_target to the semiconductor laser 5 (step ST2).

[0240] Semiconductor laser 5 emits forward laser Lf through window 8 to the outside of cover 7 by being supplied with a driving photocurrent of target value ILD_target, and emits backward laser Lb to the first optical coupler 61a and the second optical coupler 61b in optical monitor 6.

[0241] An optical monitor 6, which receives a backward-biased laser Lb, monitors the light intensity of the laser from a semiconductor laser 5 that is in a phase-reversed relationship. That is, the optical monitor 6 acquires a first monitoring value and a second monitoring value that are in an asymmetric relationship.

[0242] That is, the laser from the first optical coupler 61a that receives the backward laser Lb from the semiconductor laser 5 is incident from the first port of the input-side optical combiner / demultiplexer 62 onto the first optical waveguide 62a that constitutes the input-side optical combiner / demultiplexer 62.

[0243] On the other hand, the laser from the second optical coupler 61b that receives the backward laser Lb from the semiconductor laser 5 is incident from the third port of the input-side optical combiner / demultiplexer 62 onto the second optical waveguide 62b that constitutes the input-side optical combiner / demultiplexer 62.

[0244] The laser light from the first optical coupler 61a and the laser light from the second optical coupler 61b incident on the input-side optical multiplexer / demultiplexer 62 are split and interfered by the input-side optical multiplexer / demultiplexer 62, respectively, and propagate from the second port of the input-side optical multiplexer / demultiplexer 62 to the first asymmetric arm 63a, and from the fourth port of the input-side optical multiplexer / demultiplexer 62 to the second asymmetric arm 63b.

[0245] The laser propagating in the first asymmetric arm 63a propagates from the first port of the output-side optical wave combiner / demultiplexer 64 to the third optical waveguide 64a that constitutes the output-side optical wave combiner / demultiplexer 64.

[0246] The laser propagating in the second asymmetric arm 63b propagates from the third port of the output-side optical wave combiner / demultiplexer 64 to the fourth optical waveguide 64b that constitutes the output-side optical wave combiner / demultiplexer 64.

[0247] The laser beams propagating in the first asymmetric arm 63a and the second asymmetric arm 63b, which propagate to the output-side optical multiplexer / demultiplexer 64, are split and interfered by the output-side optical multiplexer / demultiplexer 64, respectively. The laser beams are incident from the second port of the output-side optical multiplexer / demultiplexer 64 to the first photodetector 65a, and from the fourth port of the output-side optical multiplexer / demultiplexer 64 to the second photodetector 65b.

[0248] The laser incident on the first photodetector 65a is photoelectrically converted by the first photodetector 65a, and the photocurrent representing the first monitoring value is output to the control unit 9.

[0249] The laser light incident on the second photodetector 65b is photoelectrically converted by the second photodetector 65b, and the photocurrent representing the second monitoring value is output to the control unit 9.

[0250] The relationship between the first monitoring value and the second monitoring value is as follows: Figure 7 The relationship between waveform curve A and waveform curve B is shown.

[0251] The control unit 9 converts the first monitoring value based on photocurrent into voltage, and then converts the analog value into digital value, setting it as the first monitoring value based on digital information.

[0252] The control unit 9 converts the second monitoring value based on photocurrent into voltage, and then converts the analog value into digital value, setting it as the second monitoring value based on digital information.

[0253] In addition, the conversion from photocurrent to voltage in the control unit 9 can be performed by the optical monitor 6.

[0254] In summary, the control unit 9 obtains a first monitoring value based on digital information from the output of the first photodetector 65a, and obtains a second monitoring value based on digital information from the output of the second photodetector 65b.

[0255] The control unit 9, which obtains the first and second monitoring values, calculates the optical power monitoring value Ip, which is the sum of the first and second monitoring values, the wavelength monitoring value Iλ, which is the difference between the first and second monitoring values, and the ratio of the optical power monitoring value Ip to the wavelength monitoring value Iλ, i.e., the wavelength monitoring value Iλ / Ip (step ST3).

[0256] The control unit 9 performs a determination on whether the optical power monitoring value Ip is within the range of the photocurrent setting value (step ST4).

[0257] When the optical power monitoring value Ip is outside the range of the photocurrent setting value, the control unit 9 proceeds to step ST5; when the optical power monitoring value Ip is within the range of the photocurrent setting value, it proceeds to step ST6.

[0258] The photocurrent setpoint is, for example, set to ±10% of the target value Ip_target of the optical power monitoring value Ip.

[0259] Step ST5 is the front-end temperature regulation step that controls the photocurrent supplied to the temperature regulator 2.

[0260] Step ST5 includes: a front-end temperature rise step, in which the temperature supplied by the temperature regulator 2 to the semiconductor laser 5 and the optical monitor 6 is raised when the optical power monitoring value Ip calculated by the control unit 9 in step ST3 is greater than the photocurrent setting value; and a front-end temperature fall step, in which the temperature supplied by the temperature regulator 2 to the semiconductor laser 5 and the optical monitor 6 is lowered when the optical power monitoring value Ip is less than the photocurrent setting value.

[0261] When the target value ILD_target of the driving photocurrent is supplied to the semiconductor laser 5, for example, when the optical power monitoring value Ip calculated by the control unit 9 is greater than the photocurrent setting value, it can be said that the temperature of the semiconductor laser is below 55°C.

[0262] Therefore, the control unit 9 controls the photocurrent supplied to the temperature regulator 2 by heating the mounting surface 2b of the temperature regulator 2, and returns to step ST3.

[0263] As a result, the semiconductor laser 5 and the optical monitor 6 are heated via the base 3, and the temperature of the semiconductor laser 5 and the optical monitor 6 rises to 55°C.

[0264] On the other hand, when the target value ILD_target driving photocurrent is supplied to the semiconductor laser 5, for example, if the optical power monitoring value Ip calculated by the control unit 9 in step ST3 is smaller than the photocurrent setting value, it can be said that the temperature of the semiconductor laser is higher than 55°C.

[0265] Therefore, the control unit 9 controls the photocurrent supplied to the temperature regulator 2 in a way that cools the mounting surface 2b of the temperature regulator 2, and returns to step ST3.

[0266] As a result, the semiconductor laser 5 and the optical monitor 6 are cooled via the base 3, and the temperature of the semiconductor laser 5 and the optical monitor 6 decreases to 55°C.

[0267] By repeatedly performing step ST5, the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 are adjusted by the temperature regulator 2. When the optical power monitoring value Ip calculated by the control unit 9 enters the range of the photocurrent setting value, the control unit 9 ends the previous temperature adjustment step and enters step ST6.

[0268] The wavelength locking step follows step ST6.

[0269] Similar to step ST3, step ST6 is the step of calculating the optical power monitoring value Ip, the wavelength monitoring value Iλ, and the wavelength monitoring value Iλ / Ip.

[0270] Step ST7 is the step by which the control unit 9 determines whether the optical power monitoring value Ip is within the range of the photocurrent setting value.

[0271] When the optical power monitoring value Ip is outside the range of the photocurrent setting value, the control unit 9 proceeds to step ST8; when the optical power monitoring value Ip is within the range of the photocurrent setting value, it proceeds to step ST9.

[0272] Since the optical power monitoring value Ip is within the range of the photocurrent setting value after just moving from step ST5 to step ST7, the process proceeds to step ST9.

[0273] Step ST9 is the step by which the control unit 9 determines whether the wavelength monitoring value Iλ / Ip is within the range of the wavelength setting value.

[0274] When the wavelength monitoring value Iλ / Ip is outside the range of the wavelength setting value, the control unit 9 proceeds to step ST10; when the wavelength monitoring value Iλ / Ip is within the range of the wavelength setting value, it proceeds to step ST11.

[0275] The wavelength setting value is set, for example, to ±10% of the target value Iλ_target of the wavelength monitoring value Iλ / Ip.

[0276] Step ST10 is a temperature regulation step that controls the photocurrent supplied to the temperature regulator 2.

[0277] The temperature regulation process is as follows: when the wavelength monitoring value Iλ / Ip deviates from the wavelength setting value, the temperature regulator 2 adjusts the temperature supplied to the semiconductor laser 5 and the optical monitor 6. In this example, there are the following temperature rise and temperature fall steps.

[0278] That is, step ST10 includes: a temperature rise step, in which the control unit 9 raises the temperature supplied by the temperature regulator 2 to the semiconductor laser 5 and the optical monitor 6 when the wavelength monitoring value Iλ / Ip calculated by the control unit 9 in step ST6 is greater than the wavelength setting value; and a temperature fall step, in which the control unit 9 lowers the temperature supplied by the temperature regulator 2 to the semiconductor laser 5 and the optical monitor 6 when the wavelength monitoring value Iλ / Ip is less than the wavelength setting value.

[0279] In the temperature rise step, the control unit 9 controls the photocurrent supplied to the temperature regulator 2 by heating the mounting surface 2b of the temperature regulator 2, so that the temperature of the semiconductor laser 5 and the photomonitor 6 rise, the wavelength λLD of the laser from the semiconductor laser 5 increases, and the wavelength monitoring value Iλ / Ip decreases, and returns to step ST7 via step ST6.

[0280] On the other hand, in the temperature reduction step, the control unit 9 controls the photocurrent supplied to the temperature regulator 2 in order to cool the mounting surface 2b of the temperature regulator 2, so that the temperature of the semiconductor laser 5 and the temperature of the photomonitor 6 decrease, the wavelength λLD of the laser from the semiconductor laser 5 decreases, and the wavelength monitoring value Iλ / Ip increases, and returns to step ST7 via step ST6.

[0281] During the temperature rise step in step ST10, the temperature of the semiconductor laser 5 also rises, resulting in a decrease in the light intensity of the laser light from the semiconductor laser 5 and a decrease in the optical power monitoring value Ip.

[0282] On the other hand, during the temperature decrease step in step ST10, the temperature of the semiconductor laser 5 also decreases, resulting in an increase in the light intensity of the laser from the semiconductor laser 5 and an increase in the optical power monitoring value Ip.

[0283] Therefore, when the temperature of the temperature regulator 2 is adjusted in step ST10 to adjust the wavelength λLD of the laser from the semiconductor laser 5, the optical power monitoring value Ip also changes. Therefore, in step ST7, the control unit 9 performs a determination on whether the optical power monitoring value Ip is within the range of the photocurrent setting value.

[0284] When the optical power monitoring value Ip calculated by the control unit 9 in step ST6 in step ST7 is within the range of the photocurrent setting value, step ST9 is entered, and the process is repeated from step ST10 to step ST7.

[0285] On the other hand, when the optical power monitoring value Ip calculated by the control unit 9 in step ST6 in step ST7 is outside the range of the photocurrent setting value, step ST8 is entered.

[0286] Step ST8 is the drive photocurrent control step, which controls the drive photocurrent supplied to the semiconductor laser 5.

[0287] Step ST8 includes: a driving photocurrent increase step, in which the temperature regulator 2 increases the temperature supplied to the semiconductor laser 5 and the optical monitor 6 through the temperature rise step in step ST10, and increases the driving photocurrent supplied to the semiconductor laser 5 when the optical power monitoring value Ip calculated by the control unit 9 in step ST6 is smaller than the photocurrent setting value; and a driving photocurrent decrease step, in which the temperature regulator 2 decreases the temperature supplied to the semiconductor laser 5 and the optical monitor 6 through the temperature drop step in step ST10, and decreases the driving photocurrent supplied to the semiconductor laser 5 when the optical power monitoring value Ip calculated by the control unit 9 is larger than the photocurrent setting value.

[0288] Therefore, the control unit 9 repeatedly performs step ST8 until the optical power monitoring value Ip enters the range of the photocurrent setting value. When the optical power monitoring value Ip enters the range of the photocurrent setting value, it enters step ST9 and repeatedly performs the temperature adjustment step of controlling the photocurrent supplied to the temperature regulator 2 in step ST10.

[0289] That is, the repeated cycle of temperature adjustment steps ST7-ST9-ST10-ST6-ST7-ST9 and the repeated cycle of drive photocurrent control steps ST7-ST8-ST6-ST7 are wavelength locking steps.

[0290] Through this wavelength locking step, the optical power monitoring value Ip enters the range of the photocurrent setting value, and the wavelength monitoring value Iλ / Ip enters the range of the wavelength setting value.

[0291] As a result, the semiconductor laser 5 enters a stable operation that satisfies both the condition that the light intensity in the laser from the semiconductor laser 5 is based on the target value Ip_target and the condition that the wavelength in the laser from the semiconductor laser 5 is based on the target value Iλ_target (in other words, based on the target value λ_target) of the wavelength monitoring value Iλ / Ip.

[0292] When the semiconductor laser 5 enters a stable operation, proceed to step ST11.

[0293] In step ST11, the control unit 9 continues to monitor the first monitoring value by the first photodetector 65a and the second monitoring value by the second photodetector 65b until the power supply to the optical module is cut off. It continues to monitor the optical power monitoring value Ip and the wavelength monitoring value Iλ / Ip, and continues the wavelength locking step until the power supply to the optical module is cut off. When the power supply is cut off, the wavelength locking step ends.

[0294] After the semiconductor laser 5 enters the stable operation, the semiconductor laser 5 operates using the driving photocurrent set through the wavelength locking step, and the temperature regulator 2 operates using the supply photocurrent set through the wavelength locking step, until the optical power monitoring value Ip is outside the range of the photocurrent setting value or the wavelength monitoring value Iλ / Ip is outside the range of the wavelength setting value, and then the semiconductor laser 5 continues to perform the stable operation.

[0295] When the optical power monitoring value Ip is outside the range of the photocurrent setting value or the wavelength monitoring value Iλ / Ip is outside the range of the wavelength setting value, the wavelength locking function based on the wavelength locking step is activated, and the control unit 9 performs the temperature adjustment step of step ST7-step ST9-step ST10-step ST6-step ST7-step ST9 and the drive photocurrent control step of step ST7-step ST8-step ST6-step ST7 in a cyclical manner.

[0296] As a result, the semiconductor laser 5 once again enters a stable operation that satisfies both the condition that the light intensity in the laser from the semiconductor laser 5 is based on the target value Ip_target and the condition that the wavelength in the laser from the semiconductor laser 5 is based on the target value Iλ_target of the wavelength monitoring value Iλ / Ip.

[0297] Next, the results obtained by verifying the relationship between the backward laser Lb of the semiconductor laser 5 and the first optical coupler 61a and the second optical coupler 61b when an installation offset occurs between the semiconductor laser 5 and the optical monitor 6 will be explained.

[0298] When the relationship between the backward laser Lb of the semiconductor laser 5 and the first optical coupler 61a and the second optical coupler 61b is offset, a phase difference and an optical power difference are generated between the backward laser Lb of the semiconductor laser 5 and the coupled light of the first optical coupler 61a and the second optical coupler 61b.

[0299] That is, such as Figure 10 As shown, when the central axis of the backward laser Lb of the semiconductor laser 5 is close to the first optical coupler 61a, the equiphase surface of the backward laser Lb of the semiconductor laser 5 relative to the first optical coupler 61a and the second optical coupler 61b is as follows: Figure 11 As shown.

[0300] As a result, a phase difference and optical power difference are generated between the backlight laser Lb of semiconductor laser 5 and the coupled light of the first optical coupler 61a and the coupled light of the backlight laser Lb of semiconductor laser 5 and the coupled light of the second optical coupler 61b due to the installation offset.

[0301] exist Figure 10 In the image, IS shows a schematic light distribution of the backward laser Lb of the semiconductor laser 5 relative to the first optical coupler 61a and the second optical coupler 61b.

[0302] The wavelength of the laser from the semiconductor laser 5 was set to 1.55 μm, the first optical coupler 61a and the second optical coupler 61b were set as grating couplers, and the distance between the laser emission surface of the semiconductor laser and the grating coupler was set to 0.3 mm for verification.

[0303] It was confirmed that within the assumed installation offset range, a change from 1:1 to 2:1 occurs as the power branch ratio in the coupled light between the laser of the semiconductor laser and the first optical coupler 61a and the second optical coupler 61b, and a change from 0 degrees to 150 degrees occurs as the phase difference in the coupled light between the two.

[0304] Within the assumed installation offset range, at locations where the electric field transmission coefficients t of the input-side optical multiplexer / splitter 62 and the output-side optical multiplexer / splitter 64 are 0.3, 0.5, 0.7, and 0.9 respectively, the slope of the photocurrent of the first photodetector 65a and the second photodetector 65b relative to the power branch ratio in the coupled light of the first optical coupler 61a and the second optical coupler 61b, and the slope of the output of the so-called optical monitor are estimated.

[0305] Figure 12 The estimation results are shown.

[0306] exist Figure 12 In the diagram, the upper horizontal axis shows the power branch ratio in the coupled light of the first optical coupler 61a and the second optical coupler 61b, the lower horizontal axis shows the phase difference, and the vertical axis shows the slope of the output of the optical monitor.

[0307] Lines t1 to t4 show the electric field transmission coefficient t set for the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64, respectively.

[0308] Line t1 shows the electric field transmission coefficient t = 0.3, line t2 shows the electric field transmission coefficient t = 0.5, line t3 shows the electric field transmission coefficient t = 0.7, and line t4 shows the electric field transmission coefficient t = 0.9.

[0309] For the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64, with electric field transmission coefficients t of 0.3 (t1), 0.5 (t2), 0.7 (t3), and 0.9 (t4), respectively, a total of 16 points were estimated for the power branch ratio (0.8:0.8) / phase difference 0 degrees, power branch ratio (0.9:0.7) / phase difference 45 degrees, power branch ratio (0.95:0.6) / phase difference 90 degrees, and power branch ratio (1:0.5) / phase difference 150 degrees in the coupled light of the first optical coupler 61a and the second optical coupler 61b.

[0310] according to Figure 12 It can be seen that when the electric field transmission coefficient t of the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64 is 0.7 (t3), and the power branch ratio (0.8:0.8) / phase difference is 0 degrees, i.e., the power branch ratio is 0.5, and the coupled light from the first optical coupler 61a and the second optical coupler 61b is in phase, the output slope is 0.036 GHz. -1 The maximum slope.

[0311] On the other hand, when the electric field transmission coefficient t is 0.7 (t3), the power branch ratio is (0.95:0.6) / phase difference is 90 degrees, i.e., the power branch ratio is 0.6, and the coupled light from the first optical coupler 61a and the second optical coupler 61b has a phase difference of 90 degrees, the output slope is expressed as 0.01 GHz. -1 the following.

[0312] That is, when the electric field transmission coefficient t of the input-side optical multiplexer / splitter 62 and the output-side optical multiplexer / splitter 64 is 0.7 (t3), that is, when the power branch ratio of the input-side optical multiplexer / splitter 62 and the output-side optical multiplexer / splitter 64 is 0.5, and when there is a 90-degree phase difference compared to when the coupled light with the first optical coupler 61a and the second optical coupler 61b is in the same phase, the slope of the photocurrent of the first photoreceiver 65a and the second photoreceiver 65b is significantly reduced.

[0313] On the other hand, it can be seen that when the electric field transmission coefficient t of the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64 is 0.9 (t4), within the assumed installation offset range of the coupled light between the first optical coupler 61a and the second optical coupler 61b and the input-side optical multiplexer / demultiplexer, the slope of the photocurrent of the first receiver 65a and the second receiver 65b is approximately stable at 0.025 GHz. -1 .

[0314] That is, within the range of the assumed installation offset in the coupled light of the first optical coupler 61a and the second optical coupler 61b with the input-side optical multiplexer / demultiplexer, the maximum value of the slope variation representing the allowable wavelength dependence in the photocurrent of the first photodetector 65a and the second photodetector 65b converges to within 30%.

[0315] When considering the control unit 9 located after the optical monitor 6, since the control unit 9 processes the photocurrent from the first photodetector 65a and the photocurrent from the second photodetector 65b, it is not desirable for the slope of the photocurrent from the first photodetector 65a and the second photodetector 65b to change significantly in the design. Within the assumed installation offset range in the coupled light between the first optical coupler 61a and the second optical coupler 61b and the input-side optical multiplexer / demultiplexer, the maximum value of the slope variation in the photocurrent from the first photodetector 65a and the second photodetector 65b, which represents the allowable tolerance for wavelength dependence, should be within 30%.

[0316] Therefore, it is preferable to design an optical monitor with an electric field transmission coefficient t of 0.9 for the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64 (in other words, the power branching ratio of the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64 is 0.8 (power branching ratio 2:8)).

[0317] In summary, even within the range of the assumed installation offset in the coupled light of the first optical coupler 61a and the second optical coupler 61b with the input-side optical multiplexer / demultiplexer, i.e., within the range of the assumed power branch ratio in the coupled light of the first optical coupler 61a and the second optical coupler 61b, the maximum value of the slope variation representing the tolerance for wavelength dependence in the photocurrent from the first photoreceiver 65a and the photocurrent from the second photoreceiver 65b is preferably within 30%, even if the coupling efficiency and coupling phase of the back laser Lb of the semiconductor laser 5 relative to the first optical coupler 61a and the second optical coupler 61b change.

[0318] As described above, the optical module of Embodiment 1 enables the optical monitor 6 to form an optical interferometer, which has: a first optical coupler 61a that receives laser light from the semiconductor laser 5; a second optical coupler 61b that receives laser light from the semiconductor laser 5; a first photodetector 65a that outputs a first monitoring value; and a second photodetector 65b that outputs a second monitoring value. The first path from the first optical coupler 61a to the first photodetector and the second path from the second optical coupler to the second photodetector are asymmetrical. Therefore, the optical power monitoring value Ip and the wavelength monitoring value Iλ / Ip can be obtained from the first monitoring value and the second monitoring value, and the laser light from the semiconductor laser 5 can be precisely controlled to a single wavelength.

[0319] Since the optical module of Embodiment 1 uses a first optical coupler 61a and a second optical coupler 61b compared to the one assumed optical coupler, it achieves twice the effect. Since the wavelength monitoring value Iλ is obtained by the difference between the first monitoring value and the second monitoring value, it achieves twice the effect. As a result, it obtains an optical monitor 6 with four times the sensitivity.

[0320] The optical module of Embodiment 1 enables the optical monitor 6 to have: an input-side optical multiplexer / demultiplexer 62 having a first optical waveguide 62a and a second optical waveguide 62b; a first asymmetric arm 63a composed of an optical waveguide; a second asymmetric arm 63b composed of an optical waveguide, the length of which is different from the length of the optical waveguide constituting the first asymmetric arm 63a; and an output-side optical multiplexer / demultiplexer 64 having a third optical waveguide 64a and a fourth optical waveguide 64b. Therefore, the optical monitor 6 can be constructed from a planar waveguide type optical monitor, with fewer component points, enabling miniaturization.

[0321] Since the optical module of Embodiment 1 is an optical multiplexer / demultiplexer with a power branch ratio of 0.8 for both the input-side optical multiplexer / demultiplexer 62 and the output-side optical multiplexer / demultiplexer 64, the photocurrent slopes of the first photodetector 65a and the second photodetector 65b are stable within the assumed installation offset range of the coupled light between the first optical coupler 61a and the second optical coupler 61b and the input-side optical multiplexer / demultiplexer, making the processing of the photocurrent in the control unit 9 located after the optical monitor 6 easier.

[0322] In particular, if the maximum value of the slope variation representing the tolerance for wavelength dependence in the photocurrent representing the first monitoring value output from the first photodetector 65a and the photocurrent representing the second monitoring value output from the second photodetector 65b is within 30%, then the processing of the photocurrent in the control unit 9 is easier.

[0323] Since the optical module of Embodiment 1 has a semiconductor laser 5, an optical monitor 6, a temperature regulator 2, and a base 3 arranged in the space formed by the support 1 and the cover 7, the number of pins relative to the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2 can be reduced.

[0324] Implementation method 2.

[0325] according to Figure 13 and Figure 14 This describes the optical module in Implementation Method 2.

[0326] Compared to the optical module of Embodiment 1, the optical module of Embodiment 2 has a different structure for the optical monitor 6, but is otherwise the same or identical.

[0327] That is, in the optical module of Embodiment 1, when the optical monitor 6 is configured as a planar waveguide type optical monitor based on a silicon photonic chip, the first asymmetric arm 63a and the second asymmetric arm 63b are respectively configured as waveguides (specifically, silicon waveguides) having the same group refractive index.

[0328] In contrast, the optical module of Embodiment 2 differs from the optical module of Embodiment 1 in the following aspects: when the optical monitor 6 is configured as a planar waveguide-type optical monitor based on a silicon photonic chip, the first asymmetric arm 63a and the second asymmetric arm 63b are composed of optical waveguides having common and non-common parts, the non-common part of the first asymmetric arm 63a is composed of an optical waveguide having a first group of refractive indices, and the non-common part of the second asymmetric arm 63b is composed of an optical waveguide having a second group of refractive indices that are different from the first group of refractive indices. Other aspects are the same as the optical module of Embodiment 1.

[0329] In addition, Figure 13 In, with Figure 5The same labels in the text indicate the same or equivalent parts.

[0330] Furthermore, the overall structure of the optical module is similar to that shown in Embodiment 1. Figures 1-3 They are the same, so they are omitted.

[0331] The following description focuses on the optical monitor 6 (particularly the first asymmetric arm 63a and the second asymmetric arm 63b) which is constructed from a planar waveguide optical monitor based on a silicon photonic chip.

[0332] The optical monitor 6 has a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical multiplexer / demultiplexer 64, a first optical receiver 65a, a second optical receiver 65b, and a phase adjuster 66.

[0333] Similar to the output-side optical multiplexer / splitter 64, the first light receiver 65a, and the second light receiver 65b in Embodiment 1, the output-side optical multiplexer / splitter 64, the first light receiver 65a, and the second light receiver 65b function as an interferometric measurement system for observing wavelength dependence.

[0334] The output-side optical combiner / splitter 64 is an optical circuit of the interferometric measurement system composed of the first optical receiver 65a and the second optical receiver 65b.

[0335] The optical monitor 6 is, for example, a planar waveguide-type optical monitor based on a silicon photonic chip, which is formed by integrating a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, an output-side optical multiplexer / demultiplexer 64, a first photodetector 65a, and a second photodetector 65b on a plane of a silicon (Si) substrate 6A.

[0336] The first optical coupler 61a, the second optical coupler 61b, the input-side optical multiplexer / demultiplexer 62, the output-side optical multiplexer / demultiplexer 64, the first light receiver 65a, the second light receiver 65b, and the phase adjuster 66 are all the same as the first optical coupler 61a, the second optical coupler 61b, the input-side optical multiplexer / demultiplexer 62, the output-side optical multiplexer / demultiplexer 64, the first light receiver 65a, the second light receiver 65b, and the phase adjuster 66 in the optical monitor 6 of the optical module constituting Embodiment 1.

[0337] The input node of the first asymmetric arm 63a is optically connected to the second port of the input-side optical multiplexer / demultiplexer 62, and the output node of the first asymmetric arm 63a is optically connected to the first port of the output-side optical multiplexer / demultiplexer.

[0338] The input node of the second asymmetric arm 63b is optically connected to the fourth port of the input-side optical multiplexer / demultiplexer 62, and the output node of the second asymmetric arm 63b is optically connected to the third port of the output-side optical multiplexer / demultiplexer.

[0339] like Figure 13 As shown, the first asymmetric arm 63a and the second asymmetric arm 63b are respectively composed of optical waveguides with a common part A and a non-common part B.

[0340] The first asymmetric arm 63a is composed of silicon nitride waveguides 63a1 and 63a2 and silicon waveguide 63a3.

[0341] The temperature dependence of the group refractive index n2 in a silicon nitride waveguide is different from that of the group refractive index n1 (described as n0 in Implementation 1) in a silicon waveguide.

[0342] The first asymmetric arm 63a is U-shaped. However, it is not limited to a U-shaped form.

[0343] Silicon nitride waveguide 63a1 and silicon nitride waveguide 63a2 are located at the feet of the U-shape and are arranged opposite each other.

[0344] The length (physical length) of silicon nitride waveguide 63a1 and the length (physical length) of silicon nitride waveguide 63a2 are the same.

[0345] One end of the silicon nitride waveguide 63a1 is optically connected to the second port of the input-side optical multiplexer / demultiplexer 62 via the silicon waveguide.

[0346] The other end of the silicon nitride waveguide 63a2 is optically connected to the first port of the output-side optical multiplexer / demultiplexer 64 via a silicon waveguide.

[0347] The silicon waveguide 63a3 is optically connected between the other end of the silicon nitride waveguide 63a1 and one end of the silicon nitride waveguide 63a2, located in the foldback section of the first asymmetric arm 63a.

[0348] The first asymmetric arm 63a is the optical propagation path that connects sequentially with silicon nitride waveguide 63a1, silicon waveguide 63a3, and silicon nitride waveguide 63a2 from the input node to the output node.

[0349] The first asymmetric arm 63a is symmetrical from left to right.

[0350] Silicon nitride waveguide 63a1 and silicon nitride waveguide 63a2 have a common part A and a non-common part B.

[0351] In silicon nitride waveguide 63a1, such as Figure 13As shown, the common part A is a portion of the side that is optically connected to the silicon waveguide 63a3 and a portion of the side that is optically connected to the second port of the input-side optical multiplexer / demultiplexer 62, while the non-common part B is the remaining portion of the silicon nitride waveguide 63a1, i.e., the central portion.

[0352] Similar to the common part A and the non-common part B in silicon nitride waveguide 63a1, the two ends of the common part A and the non-common part B in silicon nitride waveguide 63a2 are the common part A, and the central part is the non-common part B.

[0353] The lengths (physical lengths) of the non-common portion B in silicon nitride waveguide 63a1 and the lengths (physical lengths) of the non-common portion B in silicon nitride waveguide 63a2 are (L+ΔL) / 2, respectively.

[0354] Therefore, the non-common part B in the first asymmetric arm 63a is composed of silicon nitride waveguide with a length (physical length) of (L+ΔL).

[0355] Silicon waveguide 63a3 is the common part A.

[0356] The second asymmetric arm 63b is composed of silicon waveguides 63b1~63b3 and silicon nitride waveguides 63b4 and 63b5.

[0357] The second asymmetric arm 63b is U-shaped. However, it is not limited to a U-shaped form.

[0358] Silicon waveguide 63b1 and silicon waveguide 63b2 are located at the feet of the U-shape and are arranged opposite each other.

[0359] The length (physical length) of silicon waveguide 63b1 and the length (physical length) of silicon waveguide 63b2 are the same.

[0360] One end of the silicon waveguide 63b1 is optically connected to the fourth port of the input-side optical multiplexer / demultiplexer 62 via the silicon waveguide. Furthermore, since the silicon waveguide 63b1 and the second optical waveguide 62b of the input-side optical multiplexer / demultiplexer 62 (i.e., the silicon waveguide) are formed continuously, it is not physically possible for one end of the silicon waveguide 63b1 to be connected to the fourth port of the input-side optical multiplexer / demultiplexer 62.

[0361] The other end of silicon waveguide 63b2 is optically connected to the third port of output-side optical multiplexer / demultiplexer 64 via the silicon waveguide. Furthermore, since silicon waveguide 63b2 and the fourth optical waveguide 64b of output-side optical multiplexer / demultiplexer 64 (i.e., the silicon waveguide) are formed continuously, there is no physical connection between the other end of silicon waveguide 63b2 and the third port of output-side optical multiplexer / demultiplexer 64.

[0362] Silicon nitride waveguide 63b4 and silicon nitride waveguide 63b5 are located at the feet of the U-shape and are arranged opposite each other.

[0363] The length (physical length) of silicon nitride waveguide 63b4 and the length (physical length) of silicon nitride waveguide 63b5 are the same.

[0364] One end of silicon nitride waveguide 63b4 is optically connected to the other end of silicon waveguide 63b1.

[0365] The other end of silicon nitride waveguide 63b5 is optically connected to one end of silicon waveguide 63b2.

[0366] The silicon waveguide 63b3 is optically connected between the other end of the silicon nitride waveguide 63b4 and one end of the silicon nitride waveguide 63b5, located in the foldback section of the second asymmetric arm 63b.

[0367] The second asymmetric arm 63b is the optical propagation path that connects sequentially from the input node to silicon waveguide 63b1, silicon nitride waveguide 63b4, silicon waveguide 63b3, silicon nitride waveguide 63b5, and silicon waveguide 63b3, and reaches the output node.

[0368] The second asymmetric arm 63b is bilaterally symmetrical.

[0369] like Figure 13 As shown, silicon nitride waveguide 63b4, silicon nitride waveguide 63b5 and silicon waveguide 63b3 are the common part A relative to the first asymmetric arm 63a.

[0370] That is, the length of silicon nitride waveguide 63b4 in the second asymmetric arm 63b is the same as the length of a portion of silicon nitride waveguide 63a1 in the first asymmetric arm 63a, the length of silicon nitride waveguide 63b5 in the second asymmetric arm 63b is the same as the length of a portion of silicon nitride waveguide 63a2 in the first asymmetric arm 63a, and the length of silicon waveguide 63b3 in the second asymmetric arm 63b is the same as the length of silicon waveguide 63a3 in the first asymmetric arm 63a.

[0371] The length (physical length) of L / 2 of silicon waveguides 63b1 and 63b2 is set as the non-common part B relative to the first asymmetric arm 63a.

[0372] That is, in the second asymmetric arm 63b, the portion of silicon waveguide 63b1 and the portion of silicon waveguide 63b2 other than the common portion A located in the U-shaped fold-back section are non-common portions B.

[0373] The length (physical length) of the non-common portion B in silicon waveguide 63b1 and the length (physical length) of the non-common portion B in silicon waveguide 63b2 are L / 2, respectively.

[0374] Therefore, the non-common part B in the second asymmetric arm 63b is made of silicon waveguide with a length (physical length) of L.

[0375] The length (physical length) of the non-common part B in the first asymmetric arm 63a is longer by a length ΔL than the length (physical length) of the non-common part B in the second asymmetric arm 63b.

[0376] In the case where the optical monitor 6 is configured as a planar waveguide-type optical monitor based on a silicon photonic chip, the first path is the propagation path of light from the first port of the input-side optical multiplexer / demultiplexer 62 through the first asymmetric arm 63a composed of the input-side optical multiplexer / demultiplexer 62, silicon nitride waveguides 63a1, 63a2 and silicon waveguide 63a3 and the output-side optical multiplexer / demultiplexer 64 to the second port of the output-side optical multiplexer / demultiplexer 64.

[0377] The second path is the propagation path of light from the third port of the input-side optical multiplexer / demultiplexer 62 through the second asymmetric arm 63b composed of the input-side optical multiplexer / demultiplexer 62, silicon waveguides 63b1~63b3, silicon nitride waveguides 63b4 and 63b5, and the output-side optical multiplexer / demultiplexer 64 to the fourth port of the output-side optical multiplexer / demultiplexer 64.

[0378] Next, the method for determining the length (physical length) of the non-common part B of the first asymmetric arm 63a and the length (physical length) of the non-common part B of the second asymmetric arm 63b will be explained.

[0379] Since the common portion A of the first asymmetric arm 63a and the common portion A of the second asymmetric arm 63b have the same length and shape, the phase difference does not change even if the temperature of the common portion A of the first asymmetric arm 63a and the common portion A of the second asymmetric arm 63b changes.

[0380] The non-common part B of the first asymmetric arm 63a and the non-common part B of the second asymmetric arm 63b are made of different materials than silicon nitride waveguides and silicon waveguides, and their lengths are also different from (L+ΔL) and L.

[0381] Therefore, regarding the non-common portion B of the first asymmetric arm 63a and the non-common portion B of the second asymmetric arm 63b, the phase change due to temperature can be considered.

[0382] The coefficient of linear expansion of the substrate in the planar waveguide optical monitor is set as α.

[0383] Since the physical length L and the physical length ΔL need to be positive, they satisfy the following equation (3).

[0384] dn1 / dT+n1α>dn2 / dT+n2α (3)

[0385] The phase difference θ between the first monitored value (photocurrent from the first photodetector 65a) and the second monitored value (photocurrent from the second photodetector 65b) in the optical monitor 6 can be expressed by the following equation (4).

[0386]

[0387] In equations (3) and (4) above, n2 is the group refractive index in the silicon nitride waveguide, n1 is the group refractive index in the silicon waveguide, (L+ΔL) is the length (physical length) of the non-common part B of the first asymmetric arm 63a, L is the length (physical length) of the non-common part B of the second asymmetric arm 63b, λ is the wavelength of the backward laser Lb, and m is the coefficient connecting the wavelength λ and the optical path length nL.

[0388] In the above equation (4), n1, n2, L and ΔL are set in such a way that the temperature derivative of the above equation (4) is always 0, which is independent of temperature.

[0389] That is, when we perform temperature differentiation on the left side and set the right side to 0 in the above equation (4) to solve the above equation (4), we get the following equation (5).

[0390] Equation (5) below is obtained by making the temperature differential of equation (4) always zero, thus becoming a relationship independent of ambient temperature and operating temperature.

[0391] (5)

[0392] By satisfying the above equation (5) through the relationship between L and ΔL, if the back laser Lb from the semiconductor laser 5 does not change, the wavelength monitoring value Iλ / Ip obtained from the first monitoring value obtained from the first photodetector 65a and the second monitoring value obtained from the second photodetector 65b is not temperature dependent, and a high-precision wavelength monitoring value Iλ / Ip that does not depend on ambient temperature and operating temperature can be obtained.

[0393] Here, the group refractive index n2 can be determined by the group refractive index of the silicon nitride waveguide, and the group refractive index n1 can be determined by the group refractive index of the silicon waveguide.

[0394] That is, the parentheses in equation (5) above can determine the result.

[0395] Furthermore, the physical length ΔL can be determined by the FSR design of the Mach-Zehnder interferometer output.

[0396] Therefore, the physical length L can be obtained by the above equation (5).

[0397] In addition, if you want to increase the slope of the photocurrent from the first photodetector 65a and the slope of the photocurrent from the second photodetector 65b, you can increase ΔL to reduce the FSR caused by the FSR design. If you want to reduce the slope, you can decrease ΔL to increase the FSR.

[0398] Figure 14 The estimated results of the temperature characteristics of the optical monitor 6 are shown when the temperature is 20 degrees, 30 degrees, 40 degrees and 50 degrees.

[0399] exist Figure 14 In the diagram, the horizontal axis represents the wavelength of the backward laser Lb, and the vertical axis represents the output from the photodetector.

[0400] The temperature characteristics of waveform T1 at 20 degrees, waveform T2 at 30 degrees, waveform T3 at 40 degrees, and waveform T4 at 50 degrees are shown.

[0401] according to Figure 14 It can be seen that the waveforms T1 to T4 overlap, which enables the optical monitor 6 to obtain the first and second monitoring values ​​that are not temperature dependent.

[0402] In the aforementioned optical monitor 6, since the first asymmetric arm 63a is composed of silicon nitride waveguides 63a1, 63a2 and silicon waveguide 63a3, and the second asymmetric arm 63b is composed of silicon waveguides 63b1~63b3 and silicon nitride waveguides 63b4, 63b5, the number of connection points between waveguides with different characteristics is the same in both the first asymmetric arm 63a and the second asymmetric arm 63b. That is, in the first asymmetric arm 63a, there are a total of 4 connection points between silicon nitride waveguides 63a1, 63a2 and silicon waveguides, and in the second asymmetric arm 63b, there are a total of 4 connection points between silicon nitride waveguides 63b4, 63b5 and silicon waveguides. Therefore, the difference in propagation loss between the first asymmetric arm 63a and the second asymmetric arm 63b can be minimized.

[0403] Alternatively, the second asymmetric arm 63b can be constructed from a single silicon waveguide unit from the input node to the output node.

[0404] In this case, the common part A of the first asymmetric arm 63a and the common part A of the second asymmetric arm 63b are both made of silicon waveguides, the non-common part B of the first asymmetric arm 63a is made of silicon nitride waveguides, and the non-common part B of the second asymmetric arm 63b is made of silicon waveguides.

[0405] Even under these circumstances, the following optical monitor 6 can be achieved: by satisfying the above equation (5) through the relationship between L and ΔL, if the backward laser Lb from the semiconductor laser 5 does not change, the wavelength monitoring value Iλ / Ip obtained from the first monitoring value obtained from the first photodetector 65a and the second monitoring value obtained from the second photodetector 65b does not have temperature dependence.

[0406] Furthermore, the relationship between the first asymmetric arm 63a and the second asymmetric arm 63b can be such that the lengths of the optical waveguides in the non-common part B are different and the group refractive indices are different. It is not limited to a planar waveguide type optical monitor based on a silicon photonic chip, but can also be a planar waveguide type optical monitor using an indium phosphide substrate or a glass substrate as a compound semiconductor.

[0407] The operation of the optical module in Embodiment 2 is essentially the same as that of the optical module in Embodiment 1.

[0408] The only differences are as follows; other explanations are omitted.

[0409] That is, the laser from the first optical coupler 61a that receives the backward laser Lb from the semiconductor laser 5 is incident from the first port of the input-side optical combiner / demultiplexer 62 onto the first optical waveguide 62a that constitutes the input-side optical combiner / demultiplexer 62.

[0410] On the other hand, the laser from the second optical coupler 61b that receives the backward laser Lb from the semiconductor laser 5 is incident from the third port of the input-side optical combiner / demultiplexer 62 onto the second optical waveguide 62b that constitutes the input-side optical combiner / demultiplexer 62.

[0411] The laser light from the first optical coupler 61a and the laser light from the second optical coupler 61b incident on the input-side optical multiplexer / demultiplexer 62 are split and interfered by the input-side optical multiplexer / demultiplexer 62, respectively, and propagate from the second port of the input-side optical multiplexer / demultiplexer 62 to the first asymmetric arm 63a, and from the fourth port of the input-side optical multiplexer / demultiplexer 62 to the second asymmetric arm 63b.

[0412] The laser propagating in the first asymmetric arm 63a propagates from the first port of the output-side optical wave combiner / demultiplexer 64 to the third optical waveguide 64a that constitutes the output-side optical wave combiner / demultiplexer 64.

[0413] The laser propagating in the second asymmetric arm 63b propagates from the third port of the output-side optical wave combiner / demultiplexer 64 to the fourth optical waveguide 64b that constitutes the output-side optical wave combiner / demultiplexer 64.

[0414] The laser beams propagating in the first asymmetric arm 63a and the second asymmetric arm 63b, which propagate to the output-side optical multiplexer / demultiplexer 64, are split and interfered by the output-side optical multiplexer / demultiplexer 64, respectively. The laser beams are incident from the second port of the output-side optical multiplexer / demultiplexer 64 to the first photodetector 65a, and from the fourth port of the output-side optical multiplexer / demultiplexer 64 to the second photodetector 65b.

[0415] The laser incident on the first photodetector 65a is photoelectrically converted by the first photodetector 65a, and the photocurrent representing the first monitoring value is output to the control unit 9.

[0416] The laser light incident on the second photodetector 65b is photoelectrically converted by the second photodetector 65b, and the photocurrent representing the second monitoring value is output to the control unit 9.

[0417] The wavelength monitoring value Iλ / Ip calculated by the control unit 9 is independent of ambient temperature and operating temperature due to the action of the first asymmetric arm 63a and the second asymmetric arm 63b.

[0418] In the optical module of Embodiment 2, it was found through trial calculation that by implementing the wavelength locking step, within a temperature variation range in which the wavelength direction offset of the wavelength dependence of the wavelength dependence of the wavelength dependence of the optical power monitoring value calculated based on the photocurrent obtained from the first photodetector 65a and the photocurrent obtained from the second photodetector 65b is 100 degrees, the oscillation wavelength of the semiconductor laser 5 varies by less than 0.05 nm.

[0419] That is, within a temperature variation range of 100 degrees, the temperature dependence of the optical module in Embodiment 2 is very small when the oscillation wavelength from the semiconductor laser 5 is less than 0.05 nm.

[0420] In embodiment 2, within a temperature variation range where the wavelength direction offset of the ratio of the optical power monitoring value Ip (representing the first monitoring value) output from the first photodetector 65a and the photocurrent output from the second photodetector 65b (representing the second monitoring value) to the wavelength monitoring value Iλ (i.e., the wavelength monitoring value Iλ / Ip) is 100 degrees, the oscillation wavelength from the semiconductor laser 5 can be below 0.1 nm, enabling precise control of the laser from the semiconductor laser 5.

[0421] As described above, similar to the optical module of Embodiment 1, the optical module of Embodiment 2 can precisely control the laser from the semiconductor laser 5 to a single wavelength, has fewer components, and can be miniaturized.

[0422] Furthermore, since the optical module of Embodiment 2 is configured such that the lengths of the non-common portions B in the first asymmetric arm 63a and the non-common portions B in the second asymmetric arm 63b are different, and the group refractive indices are different, by appropriately selecting the length and group refractive index of the non-common portions B, the wavelength monitoring value Iλ / Ip obtained from the first monitoring value obtained from the first photodetector 65a and the second monitoring value obtained from the second photodetector 65b can be set as a wavelength monitoring value that is not temperature dependent.

[0423] Implementation method 3.

[0424] according to Figure 15 and Figure 16 This describes the optical module in Implementation Method 3.

[0425] Compared to the optical module of Embodiment 2, the optical module of Embodiment 3 has a different structure for the optical monitor 6, but is otherwise the same or identical.

[0426] That is, in the optical module of Embodiment 2, when the optical monitor 6 is configured by a planar waveguide type optical monitor based on a silicon photonic chip, the optical circuit after the first asymmetric arm 63a and the second asymmetric arm 63b is configured with an output-side optical multiplexer / demultiplexer 64, a first light receiver 65a and a second light receiver 65b, and further with a phase adjuster 66.

[0427] In contrast, the optical module of Embodiment 3, when configured as an optical monitor 6 using a planar waveguide-type optical monitor based on a silicon photonic chip, differs from the optical module of Embodiment 2 in that the optical circuits after the first asymmetric arm 63a and the second asymmetric arm 63b have a structure with a 90-degree hybrid structure optical circuit OC, a structure with a first light-receiving part 65a and a second light-receiving part 65b, and a structure without a phase adjuster 66. Other aspects are the same as those of the optical module of Embodiment 2.

[0428] That is, in Embodiment 2, the output-side optical combiner / splitter 64, the first light receiver 65a, and the second light receiver 65b function as an interferometric measurement system for observing wavelength dependence. In contrast, in Embodiment 3, the 90-degree hybrid structured optical loop OC, the first light receiver 65a, and the second light receiver 65b function as an interferometric measurement system for observing wavelength dependence. This is the difference. In other respects, Embodiment 3 is the same as Embodiment 2.

[0429] The 90-degree hybrid structured optical loop OC is an optical loop of the interferometric measurement system composed of the first photodetector 65a and the second photodetector 65b.

[0430] In addition, Figure 15 In, with Figure 13The same labels in the text indicate the same or equivalent parts.

[0431] Furthermore, similar to Embodiment 2, the overall structure of the optical module is the same as that shown in Embodiment 1. Figures 1-3 They are the same, so they are omitted.

[0432] The following description focuses on the optical monitor 6, which is constructed from a planar waveguide optical monitor based on a silicon photonic chip (especially the optical loops after the first asymmetric arm 63a and the second asymmetric arm 63b, i.e., the optical loops that function as an interferometric measurement system for observing wavelength dependence).

[0433] The optical monitor 6 has a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, a 90-degree hybrid structured optical loop OC, a first light-receiving section 65a, and a second light-receiving section 65b.

[0434] The optical monitor 6 is, for example, a planar waveguide type optical monitor based on a silicon photonic chip. This planar waveguide type optical monitor is formed by integrating a first optical coupler 61a, a second optical coupler 61b, an input-side optical multiplexer / demultiplexer 62, a first asymmetric arm 63a, a second asymmetric arm 63b, a 90-degree hybrid structure optical loop OC, a first light-receiving part 65a, and a second light-receiving part 65b on the plane of a silicon substrate 6A.

[0435] The first optical coupler 61a, the second optical coupler 61b, the input-side optical multiplexer / demultiplexer 62, the first asymmetric arm 63a, and the second asymmetric arm 63b are each identical to the first optical coupler 61a, the second optical coupler 61b, the input-side optical multiplexer / demultiplexer 62, the first asymmetric arm 63a, and the second asymmetric arm 63b in the optical monitor 6 of the optical module constituting Embodiment 2.

[0436] The 90-degree hybrid structured light loop OC has a first input node, a second input node, a first output node, and a second output node. The first input node is optically connected to the output node of the first asymmetric arm 63a, and the second input node is optically connected to the output node of the second asymmetric arm 63b. The I-axis is output to the first output node, and the Q-axis is output to the second output node.

[0437] In this example, the I-use light output consists of the first I-use output light and the second I-use output light.

[0438] In this example, the Q-light output consists of the first Q-light output and the second Q-light output.

[0439] The first light-receiving unit 65a receives the I-beam output from the first output node of the 90-degree hybrid structured optical loop OP, and outputs... Figure 16 The I signal shown is the first monitoring value.

[0440] exist Figure 16 In the I signal shown, the horizontal axis represents the wavelength of the backward laser Lb, and the vertical axis represents the output from the first light-receiving unit 65a.

[0441] The first light-receiving unit 65a has a first-type light receiver 65a1 and a second-type light receiver 65a2 connected in series between a power supply potential node for the light-receiving unit and a ground node. In this case, the first light-receiving unit 65a, which includes the first-type light receiver 65a1 and the second-type light receiver 65a2, is also included as the first light receiver.

[0442] The first photodetector 65a1 receives the first output light from the 90-degree hybrid structured optical loop OC.

[0443] The second-stage receiver 65a2 receives the second-stage output light from the 90-degree hybrid structured optical loop OC.

[0444] The I signal, i.e. the first monitoring value, is output to the connection point of the first I light receiver 65a1 and the second I light receiver 65a2.

[0445] The second light-receiving unit 65b receives the Q-band light output from the second output node of the 90-degree hybrid structured optical loop OP, and outputs... Figure 16 The Q signal shown is the second monitoring value.

[0446] exist Figure 16 In the Q signal shown, the horizontal axis represents the wavelength of the backward laser Lb, and the vertical axis represents the output from the second light-receiving unit 65b.

[0447] There is a 90-degree phase difference between the Q signal and the I signal.

[0448] The second light-receiving section 65b has a first Q light receiver 65b1 and a second Q light receiver 65b2 connected in series between the power supply potential node and the ground node of the light-receiving section. In this case, a second light-receiving section 65b having the first Q light receiver 65b1 and the second Q light receiver 65b2 is also included as a second light receiver.

[0449] The first Q-type receiver 65b1 receives the first Q-type output light from the 90-degree hybrid structured optical loop OC.

[0450] The second Q receiver 65b2 receives the second Q output light from the 90-degree hybrid structured optical loop OC.

[0451] The Q signal, i.e. the second monitoring value, is output to the connection point of the first Q receiver 65b1 and the second Q receiver 65b2.

[0452] The 90-degree hybrid structured optical loop OC has a first 1×2 optical wave combiner / demultiplexer 67a, a second 1×2 optical wave combiner / demultiplexer 67b, a first 2×2 optical wave combiner / demultiplexer 68a, a second 2×2 optical wave combiner / demultiplexer 68b, and a 90-degree delayer 69.

[0453] The first 1×2 optical wave combiner / demultiplexer 67a has ports 1 to 3.

[0454] The first port of the first 1×2 optical combiner / demultiplexer 67a is optically connected to the output node of the first asymmetric arm 63a.

[0455] The first 1×2 optical combiner / demultiplexer 67a splits the optical output from the first asymmetric arm 63a into two optical outputs.

[0456] The first 1×2 optical wave combiner / demultiplexer 67a can be, for example, any of a directional coupler, an MMI waveguide, and a Y-branch waveguide. In this example, an MMI waveguide is used as the first 1×2 optical wave combiner / demultiplexer 67a.

[0457] Furthermore, the first port of the first 1×2 optical wave combiner / demultiplexer 67a and the output node of the first asymmetric arm 63a are not physically separated, but are connected to the silicon waveguide of the first port of the first 1×2 optical wave combiner / demultiplexer 67a and the first asymmetric arm 63a in a continuous manner.

[0458] The second 1×2 optical combiner / demultiplexer 67b has ports 1 through 3.

[0459] The first port of the second 1×2 optical combiner / demultiplexer 67b is optically connected to the output node of the second asymmetric arm 63b.

[0460] The second 1×2 optical combiner / demultiplexer 67b splits the optical output from the second asymmetric arm 63b into two optical outputs.

[0461] The second 2×2 optical wave combiner / demultiplexer 67b can be, for example, any of a directional coupler, an MMI waveguide, and a Y-branch waveguide. In this example, an MMI waveguide is used as the second 2×2 optical wave combiner / demultiplexer 67b.

[0462] Furthermore, the output nodes of the first port of the second 2×2 optical wave combiner / demultiplexer 67b and the second asymmetric arm 63b are not physically separated, but are continuously connected to form the connection point of the silicon waveguide of the first port of the second 2×2 optical wave combiner / demultiplexer 67b and the second asymmetric arm 63b.

[0463] The 90-degree delay unit 69 delays the input light output by 90 degrees, that is, the phase changes by 90 degrees before the output.

[0464] The input node of the 90-degree delay unit 69 is optically connected to the third port of the second 1×2 optical multiplexer / demultiplexer 67b.

[0465] The 90-degree delayer 69 is composed of an optical waveguide.

[0466] Furthermore, the input node of the 90-degree delayer 69 and the third port of the second 1×2 optical wave combiner / demultiplexer 73b are not physically separated, but are continuously formed as the connection point of the silicon waveguide that constitutes the output side of the optical waveguide of the other side of the 90-degree delayer 69 and the second 1×2 optical wave combiner / demultiplexer 67b.

[0467] The first 2×2 optical wave combiner / demultiplexer 68a has ports 1 to 4, a fifth optical waveguide connecting ports 1 and 2, and a sixth optical waveguide connecting ports 3 and 4.

[0468] In the first 2×2 optical wave combiner / demultiplexer 68a, the first port is optically connected to the second port of the first 1×2 optical wave combiner / demultiplexer 67a, and the third port is optically connected to the second port of the second 1×2 optical wave combiner / demultiplexer 67b.

[0469] The fifth and sixth optical waveguides in the first 2×2 optical wave combiner / demultiplexer 68a are silicon waveguides.

[0470] The length of the 5th optical waveguide is the same as the length of the 6th optical waveguide.

[0471] The first 2×2 optical wave combiner / demultiplexer 68a is an asymmetric optical wave combiner / demultiplexer, and in this example, for example, the power split ratio is set to 0.8. In other words, the power split ratio relative to the 5th and 6th optical waveguides is set to 2:8.

[0472] Furthermore, the first port of the first 2×2 optical wave combiner / demultiplexer 68a and the second port of the first 1×2 optical wave combiner / demultiplexer 67a are not physically separate, but are connected continuously to form the connection point of the silicon waveguide that constitutes the fifth optical waveguide of the first 2×2 optical wave combiner / demultiplexer 68a and the output side optical waveguide of one of the first 1×2 optical wave combiners / demultiplexers 67a.

[0473] Furthermore, the third port of the first 2×2 optical wave combiner / demultiplexer 68a and the second port of the second 2×2 optical wave combiner / demultiplexer 67b are not physically separate, but are continuously connected to form the connection point of the silicon waveguides that constitute the sixth optical waveguide of the second 2×2 optical wave combiner / demultiplexer 67b and the output side optical waveguide of one of the second 1×2 optical wave combiners / demultiplexers 67a.

[0474] The first 2×2 optical wave combiner / demultiplexer 68a can be, for example, any one of a directional coupler, an MMI waveguide, and a Y-branch waveguide. In this example, an MMI waveguide is used as the first 2×2 optical wave combiner / demultiplexer 68a.

[0475] The second 2×2 optical wave combiner / demultiplexer 68b has ports 1 to 4, a 7th optical waveguide connecting ports 1 and 2, and an 8th optical waveguide connecting ports 3 and 4.

[0476] In the second 2×2 optical multiplexer / demultiplexer 68b, the first port is optically connected to the third port of the first 1×2 optical multiplexer / demultiplexer 67a, and the third port is optically connected to the output node of the 90-degree delayer 69.

[0477] The 7th and 8th optical waveguides in the second 2×2 optical wave combiner / demultiplexer 68b are silicon waveguides.

[0478] The length of the 7th optical waveguide is the same as the length of the 8th optical waveguide.

[0479] The second 2×2 optical wave combiner / demultiplexer 68b is an asymmetric optical wave combiner / demultiplexer, in this example, for example, with the power split ratio set to 0.8. In other words, the power split ratio relative to the 7th and 8th optical waveguides is set to 2:8.

[0480] Furthermore, the first port of the second 2×2 optical wave combiner / demultiplexer 68b and the third port of the first 1×2 optical wave combiner / demultiplexer 67a are not physically separate, but are continuously connected to form the connection point of the silicon waveguide that constitutes the seventh optical waveguide of the second 2×2 optical wave combiner / demultiplexer 68b and the optical waveguide that constitutes the output side of the first 1×2 optical wave combiner / demultiplexer 67a.

[0481] Furthermore, the third port of the second 2×2 optical wave combiner / demultiplexer 68b and the output node of the 90-degree delayer 69 are not physically separated, but are continuously connected to form the connection point of the eighth optical waveguide constituting the second 2×2 optical wave combiner / demultiplexer 68b and the silicon waveguide constituting the optical waveguide of the 90-degree delayer 69.

[0482] The second 2×2 optical wave combiner / demultiplexer 68b can be, for example, any of a directional coupler, an MMI waveguide, and a Y-branch waveguide. In this example, an MMI waveguide is used as the second 2×2 optical wave combiner / demultiplexer 68b.

[0483] In the first photodetector 65a1 that constitutes the first light-receiving section 65a, the anode electrode is connected to the power supply potential node of the light-receiving section, and the cathode electrode is connected to the first output terminal of the optical monitor 6 that outputs the first monitoring value.

[0484] In the second photodetector 65a2 constituting the first photodetector 65a, the anode electrode is connected to the first output terminal, and the cathode electrode is connected to the grounding node.

[0485] In the first Q photodetector 65b1 that constitutes the second light-receiving section 65b, the anode electrode is connected to the light-receiving section via a power supply potential node, and the cathode electrode is connected to the second output terminal of the optical monitor 6 that outputs the second monitoring value.

[0486] In the second Q photodetector 65b2 that constitutes the second light-receiving section 65b, the anode electrode is connected to the second output terminal, and the cathode electrode is connected to the grounding node.

[0487] The first I photodetector 65a1 and the second I photodetector 65a2, and the first Q photodetector 65b1 and the second Q photodetector 65b2 are waveguide type photodetectors or surface incident type photodetectors, respectively. In this example, a photodiode is used as a SiGe photodetector.

[0488] The relationship between semiconductor laser 5, optical monitor 6, temperature regulator 2 and pins P1~P6 is explained.

[0489] Pin P1 is the main signal pin relative to semiconductor laser 5.

[0490] Pin P2 is a monitoring pin connected to the first output terminal of optical monitor 6, and is used for monitoring relative to the first monitoring pin of optical monitor 6.

[0491] Pin P3 is a second monitoring pin connected to the second output terminal of optical monitor 6, relative to the second monitoring pin of optical monitor 6.

[0492] Pins P4 and P5 are a pair of temperature control pins relative to temperature regulator 2.

[0493] Pin P6 is a power supply pin used to supply power to the first light-receiving unit 65a and the second light-receiving unit 65b, and is connected to the anode electrode of the first I light-receiving unit 65a1 and the anode electrode of the first Q light-receiving unit 65b1. Pin P6 is a power supply pin for the light-receiving unit and also serves as a power supply potential node for the light-receiving unit.

[0494] Pin P7 is the ground pin.

[0495] The optical module in Implementation 3 also only requires a total of 7 pins: 6 signal pins P1 to P6 and 1 ground pin P7 for each structural element. The optical module can be constructed with a smaller number of pins.

[0496] As a result, miniaturization can be achieved using a standard CAN package with a diameter of 5.6mm and a maximum of 7 pins.

[0497] Next, the operation of the optical module in Embodiment 3 will be explained.

[0498] Regarding the prior preparation for activating the optical module, similar to the prior preparation for the optical module in Embodiments 1 and 2, the target value ILD_target of the driving photocurrent supplied to the semiconductor laser 5, the target value ITEC_target of the photocurrent supplied to the temperature regulator 2, the target value Ip_target of the optical power monitoring value Ip, and the target value Iλ_target of the wavelength monitoring value Iλ / Ip when the wavelength λLD is set to the target value λ_target are obtained.

[0499] When the optical module is started, the driving photocurrent of the target value ILD_target is supplied to the semiconductor laser 5 in the same way as the optical modules in Embodiment 1 and Embodiment 2 (step ST2).

[0500] Semiconductor laser 5 emits forward laser Lf through window 8 to the outside of cover 7 by being supplied with a driving photocurrent of target value ILD_target, and emits backward laser Lb to the first optical coupler 61a and the second optical coupler 61b in optical monitor 6.

[0501] The laser from the first optical coupler 61a that receives the backward laser Lb from the semiconductor laser 5 is incident from the first port of the input-side optical combiner / demultiplexer 62 onto the first silicon waveguide 62a that constitutes the input-side optical combiner / demultiplexer 62.

[0502] On the other hand, the laser from the second optical coupler 61b that receives the backward laser Lb from the semiconductor laser 5 is incident from the third port of the input-side optical combiner / demultiplexer 62 onto the second optical waveguide 62b that constitutes the input-side optical combiner / demultiplexer 62.

[0503] The laser light from the first optical coupler 61a and the laser light from the second optical coupler 61b incident on the input-side optical multiplexer / demultiplexer 62 are split and interfered by the input-side optical multiplexer / demultiplexer 62, respectively, and propagate from the second port of the input-side optical multiplexer / demultiplexer 62 to the first asymmetric arm 63a, and from the fourth port of the input-side optical multiplexer / demultiplexer 62 to the second asymmetric arm 63b.

[0504] The laser propagating in the first asymmetric arm 63a is incident on the first input node of the 90-degree hybrid structured light loop OC as the first incident light.

[0505] The laser propagating in the second asymmetric arm 63b is input to the second input node of the 90-degree hybrid structured light loop OC as the second incident light.

[0506] In a 90-degree hybrid structured optical loop (OC), the first incident light input to the first input node is split into the first branch light and the second branch light by the first 1×2 optical combiner / demultiplexer 67a, and the second incident light input to the second input node is split into the third branch light and the fourth branch light by the second 1×2 optical combiner / demultiplexer 67b.

[0507] The first branch light is incident from the first port of the first 2×2 optical wave combiner / demultiplexer 68a to the fifth optical waveguide that constitutes the first 2×2 optical wave combiner / demultiplexer 68a.

[0508] On the other hand, the third branch light is incident from the third port of the first 2×2 optical wave combiner / demultiplexer 68a to the sixth optical waveguide constituting the first 2×2 optical wave combiner / demultiplexer 68a.

[0509] The first and third branch beams incident on the first 2×2 optical wave combiner / splitter 68a are split and interfered by the first 2×2 optical wave combiner / splitter 68a, respectively. They are emitted from the second port of the first 2×2 optical wave combiner / splitter 68a to the first I light receiver 65a1 constituting the first light receiving section 65a, and serve as the first I output beam. They are emitted from the fourth port of the first 2×2 optical wave combiner / splitter 68a to the second I light receiver 65a2 constituting the first light receiving section 65a, and serve as the second I output beam.

[0510] The first output light is photoelectrically converted by the first photodetector 65a1, and the second output light is photoelectrically converted by the second photodetector 65a2. A photocurrent flows through the first and second photodetectors 65a1 and 65a2, and an output light appears at the connection point between the first and second photodetectors 65a1 and 65a2, i.e., the first output terminal. Figure 16 The I signal is shown.

[0511] The I signal represents the first monitoring value of the analog photocurrent and is input to the control unit 9.

[0512] The second branch light is incident from the first port of the second 2×2 optical wave combiner / demultiplexer 68b to the seventh optical waveguide that constitutes the second 2×2 optical wave combiner / demultiplexer 68b.

[0513] On the other hand, the fourth branch light is delayed by 90 degrees by the 90-degree delayer 69 and is incident from the third port of the second 2×2 optical wave combiner / demultiplexer 68b to the eighth optical waveguide that constitutes the second 2×2 optical wave combiner / demultiplexer 68b.

[0514] The second branch light incident on the second 2×2 optical wave combiner / splitter 68b and the fourth branch light delayed by 90 degrees are split and interfered by the second 2×2 optical wave combiner / splitter 68b, respectively. They are emitted from the second port of the second 2×2 optical wave combiner / splitter 68b to the first Q light receiver 65b1 constituting the second light receiving section 65b, and are emitted from the fourth port of the second 2×2 optical wave combiner / splitter 68b to the second Q light receiver 65b2 constituting the second light receiving section 65b, and are emitted as the second Q light output.

[0515] The first to third branches of the light do not undergo phase changes, while the fourth branch is delayed by 90 degrees by a 90-degree delayer 69, i.e., its phase changes by 90 degrees.

[0516] The first Q output light is photoelectrically converted by the first Q receiver 65b1, and the second Q output light is photoelectrically converted by the second Q receiver 65b2. A photocurrent flows through the first Q receiver 65b1 and the second Q receiver 65b2, and an output current appears at the connection point between the first Q receiver 65b1 and the second Q receiver 65b2, i.e., the first output terminal. Figure 16 The Q signal is shown.

[0517] The Q signal is 90 degrees out of phase with respect to the I signal.

[0518] The Q signal has a 90-degree phase change relative to the I signal, which is the second monitoring value representing the analog photocurrent, and is input to the control unit 9.

[0519] like Figure 16 As shown, the trajectory point can be mapped onto the IQ plane using the analog photocurrent (I signal) representing the first monitoring value and the analog photocurrent (Q signal) representing the second monitoring value.

[0520] exist Figure 16 In the constellation diagram shown, the I-axis indicates the magnitude of the I signal, which represents the value of the analog photocurrent for the first monitoring value, and the Q-axis indicates the magnitude of the Q signal, which represents the value of the analog photocurrent for the second monitoring value.

[0521] If the optical power of the backward laser Lb of the semiconductor laser 5 is fixed, the trajectory point rotates on a circle with a fixed radius corresponding to the optical power, depending on the wavelength change of the backward laser Lb.

[0522] If the optical power increases, the radius of the circle increases; if the optical power decreases, the radius of the circle decreases.

[0523] Therefore, by knowing the location of the trajectory points based on the first and second monitoring values ​​from the center on the constellation diagram, the optical power monitoring value Ip can be obtained.

[0524] On the other hand, when the wavelength of the backward laser Lb of the semiconductor laser 5 changes, the angle of the radius vector formed by the trajectory point changes.

[0525] Therefore, by knowing the angle of the line segment connecting the center of the constellation diagram to the position of the trajectory point based on the first and second monitoring values ​​relative to the I-axis, the wavelength can be obtained using the monitoring value Iλ.

[0526] By obtaining the optical power monitoring value Ip and the wavelength monitoring value Iλ, the wavelength monitoring value Iλ / Ip can be obtained (step ST3a).

[0527] That is, since the change in wavelength of the backward laser Lb is proportional to the rotation of the trajectory point, the change in wavelength of the backward laser Lb can be observed seamlessly without the need for separate phase adjustment of the optical monitor 6.

[0528] The control unit 9 converts the first monitoring value based on photocurrent into voltage, and then converts the analog value into digital value, setting it as the first monitoring value based on digital information. It converts the second monitoring value based on photocurrent into voltage, and then converts the analog value into digital value, setting it as the second monitoring value based on digital information. Compared with the constellation diagram obtained in advance and stored in the storage unit, it obtains the optical power monitoring value Ip, the wavelength monitoring value Iλ, and the wavelength monitoring value Iλ / Ip.

[0529] Regarding the actions of the control unit 9 after obtaining the optical power monitoring value Ip, the wavelength monitoring value Iλ, and the wavelength monitoring value Iλ / Ip, similar to the actions of the optical modules in Embodiment 1 and Embodiment 2, the actions after step ST4 are performed, including adjusting the temperature of the semiconductor laser, adjusting the light output from the semiconductor laser, and adjusting the oscillation wavelength.

[0530] As described above, similar to the optical modules of Embodiments 1 and 2, the optical module of Embodiment 3 can precisely control the laser from the semiconductor laser 5 to a single wavelength, has fewer components, and can be miniaturized.

[0531] Furthermore, similar to the optical module of Embodiment 2, the optical module of Embodiment 3 can set the wavelength monitoring value Iλ / Ip obtained from the first monitoring value obtained from the first light-receiving unit 65a and the second monitoring value obtained from the second light-receiving unit 65b to a wavelength monitoring value that is not temperature-dependent in the optical monitor 6.

[0532] Furthermore, the optical module of Embodiment 3 can obtain high-precision optical power monitoring value Ip, wavelength monitoring value Iλ, and wavelength monitoring value Iλ / Ip without performing phase adjustment on the optical monitor 6.

[0533] In the optical module of Embodiment 3, similarly to the optical module of Embodiment 2, the first asymmetric arm 63a is formed by silicon nitride waveguides 63a1, 63a2 and silicon waveguide 63a3, and the second asymmetric arm 63b is formed by silicon waveguides 63b1~63b3 and silicon nitride waveguides 63b4, 63b5. However, similarly to the optical module of Embodiment 1, the first asymmetric arm 63a and the second asymmetric arm 63b can also be formed by silicon waveguide units respectively.

[0534] The optical module in Implementation 3 is not limited to a planar waveguide optical monitor based on a silicon photonic chip, but can also be a planar waveguide optical monitor using an indium phosphide substrate or a glass substrate as a compound semiconductor.

[0535] Furthermore, it is possible to freely combine the various embodiments, or modify any structural elements of the various embodiments, or omit any structural elements in the various embodiments.

[0536] Industrial availability

[0537] The optical module disclosed herein is suitable for use in high-capacity optical communication systems, particularly optical modules used in digital coherent communication methods.

[0538] Label Explanation

[0539] 1: Support; 2: Temperature regulator; 3: Base; 4: Sub-mount for semiconductor laser; 5: Semiconductor laser; 6: Optical monitor (planar waveguide type optical monitor); 61a: First optical coupler; 61b: Second optical coupler; 62: Input-side optical multiplexer / demultiplexer; 63a: First asymmetric arm; 63b: Second asymmetric arm; 64: Output-side optical multiplexer / demultiplexer; 65a: First photodetector; 65b: Second photodetector; 66: Phase adjuster; 7: Cover; 8: Window; 9: Control unit; 10: Package; P1~P7: Pins.

Claims

1. An optical module, wherein, This optical module has the following features: Semiconductor lasers; as well as An optical monitor receives laser light from the semiconductor laser and outputs first and second monitoring values ​​for estimating the intensity and wavelength of the laser light from the semiconductor laser. The optical monitor constitutes an optical interferometer, which includes: a first optical coupler that receives laser light from the semiconductor laser; a second optical coupler that receives laser light from the semiconductor laser; and a first light receiver that outputs the first monitoring value. And a second light receiver, which outputs the second monitoring value, wherein the first path from the first optical coupler to the first light receiver and the second path from the second optical coupler to the second light receiver are asymmetrical.

2. The optical module according to claim 1, wherein, The optical interferometer in the optical monitor has: An input-side optical multiplexer / demultiplexer has ports 1 to 4, with port 1 coupled to the first optical coupler and port 3 coupled to the second optical coupler. The first asymmetric arm is composed of an optical waveguide that is optically connected to the second port of the input-side optical multiplexer / demultiplexer. The second asymmetric arm is composed of an optical waveguide that is optically connected to the fourth port of the input-side optical multiplexer / demultiplexer. The physical length of this optical waveguide is different from the physical length of the optical waveguide that constitutes the first asymmetric arm. as well as An output-side optical multiplexer / demultiplexer has ports 1 through 4. Port 1 is optically connected to the output node of the first asymmetric arm, port 3 is optically connected to the output node of the second asymmetric arm, port 2 is coupled to the first optical receiver, and port 4 is coupled to the second optical receiver. The first path is the propagation path of light from the first port of the input-side optical multiplexer / demultiplexer, through the input-side optical multiplexer / demultiplexer, the first asymmetric arm, and the output-side optical multiplexer / demultiplexer, to the second port of the output-side optical multiplexer / demultiplexer. The second path is the propagation path of light from the second port of the input-side optical multiplexer / demultiplexer, through the input-side optical multiplexer / demultiplexer, the second asymmetric arm, and the output-side optical multiplexer / demultiplexer to the fourth port of the output-side optical multiplexer / demultiplexer.

3. An optical module, wherein, This optical module has the following features: Semiconductor lasers; as well as An optical monitor receives laser light from the semiconductor laser and outputs first and second monitoring values ​​for estimating the intensity and wavelength of the laser light from the semiconductor laser. The optical monitor includes: a first optical coupler for receiving laser light from the semiconductor laser; a second optical coupler for receiving laser light from the semiconductor laser; a first light receiver for outputting the first monitoring value; a second light receiver for outputting the second monitoring value; and an optical interferometer. The optical interferometer has the following features: An input-side optical multiplexer / demultiplexer has ports 1 to 4, with port 1 coupled to the first optical coupler and port 3 coupled to the second optical coupler. The first asymmetric arm is composed of an optical waveguide that is optically connected to the second port of the input-side optical multiplexer / demultiplexer. The second asymmetric arm is composed of an optical waveguide that is optically connected to the fourth port of the input-side optical multiplexer / demultiplexer. The physical length of this optical waveguide differs from the physical length of the optical waveguide constituting the first asymmetric arm. An optical loop having a first input node, a second input node, a first output node, and a second output node, wherein the first input node is optically connected to the output node of the first asymmetric arm, the second input node is optically connected to the output node of the second asymmetric arm, the first output node is optically coupled to the first photodetector, and the second output node is optically coupled to the second photodetector, the optical loop being used to form an interferometric measurement system for observing wavelength dependence through the first and second photodetectors.

4. The optical module according to claim 3, wherein, The optical waveguide in the first asymmetric arm has a common portion and a non-common portion, the non-common portion being an optical waveguide with a first-group refractive index. The optical waveguide in the second asymmetric arm has a common part and a non-common part. The optical waveguide in the non-common part is an optical waveguide with a second group refractive index, which has a temperature dependence of a group refractive index that is different from that of the first group refractive index.

5. An optical module, wherein, This optical module has the following features: Semiconductor lasers; as well as An optical monitor receives laser light from the semiconductor laser and outputs first and second monitoring values ​​for estimating the intensity and wavelength of the laser light from the semiconductor laser. The optical monitor includes: a first optical coupler for receiving laser light from the semiconductor laser; a second optical coupler for receiving laser light from the semiconductor laser; a first light receiver for outputting the first monitoring value; a second light receiver for outputting the second monitoring value; and an optical interferometer. The optical interferometer has the following features: An input-side optical multiplexer / demultiplexer has ports 1 to 4, with port 1 coupled to the first optical coupler and port 3 coupled to the second optical coupler. The first asymmetric arm has an input node that is optically connected to the second port of the input-side optical combiner / demultiplexer, and has a common part of the optical waveguide and a non-common part of the optical waveguide. The non-common part of the optical waveguide is an optical waveguide with a first group of refractive indices. The second asymmetric arm has its input node optically connected to the fourth port of the input-side optical combiner / demultiplexer. It has a common portion of optical waveguide and a non-common portion of optical waveguide. The non-common portion of optical waveguide is an optical waveguide with a second group refractive index. The second group refractive index has a temperature dependence of the group refractive index, which is different from the first group refractive index. The physical length of the non-common portion is different from the physical length of the non-common portion of the optical waveguide in the first asymmetric arm. as well as An optical loop having a first input node, a second input node, a first output node, and a second output node, wherein the first input node is optically connected to the output node of the first asymmetric arm, the second input node is optically connected to the output node of the second asymmetric arm, the first output node is optically coupled to the first photodetector, and the second output node is optically coupled to the second photodetector, the optical loop being used to form an interferometric measurement system for observing wavelength dependence through the first and second photodetectors.

6. The optical module according to any one of claims 3 to 5, wherein, The optical circuit used to constitute the interferometric measurement system is an output-side optical combiner / demultiplexer, which has a first port to a fourth port. The first port is the first input node of the optical circuit, the second port is the first output node of the optical circuit, the third port is the second input node of the optical circuit, and the fourth port is the second output node of the optical circuit.

7. The optical module according to claim 6, wherein, The input-side optical multiplexer / demultiplexer is an optical multiplexer / demultiplexer with a power branch ratio of 2:

8. The output-side optical combiner / demultiplexer is an optical combiner / demultiplexer with a power branching ratio of 2:

8.

8. The optical module according to claim 6, wherein, Within the assumed installation offset range of the coupled light of the first optical coupler and the second optical coupler with the input-side optical multiplexer / demultiplexer, the maximum value of the slope variation representing the tolerance for wavelength dependence in the photocurrent representing the first monitoring value output from the first photodetector and the photocurrent representing the second monitoring value output from the second photodetector is within 30%.

9. The optical module according to claim 6, wherein, Within a temperature variation range where the wavelength direction offset of the wavelength-dependent wavelength monitoring value is 100 degrees, the oscillation wavelength from the semiconductor laser is less than 0.1 nm. The wavelength monitoring value is the ratio of the optical power monitoring value to the wavelength monitoring value, calculated based on the photocurrent representing the first monitoring value output from the first photodetector and the photocurrent representing the second monitoring value output from the second photodetector.

10. The optical module according to claim 6, wherein, The optical monitor is a planar waveguide-type optical monitor based on a silicon photonic chip. This silicon photonic chip is formed by integrating the first optical coupler, the second optical coupler, the input-side optical multiplexer / demultiplexer, the first asymmetric arm, the second asymmetric arm, the output-side optical multiplexer / demultiplexer, the first light receiver, and the second light receiver on a plane of a silicon substrate. The first optical coupler and the second optical coupler are grating couplers, respectively.

11. The optical module according to claim 5, wherein, The optical circuit used to construct the interferometric measurement system is an output-side optical multiplexer / demultiplexer, which has ports 1 to 4. Port 1 is the first input node of the optical circuit, port 2 is the first output node of the optical circuit, port 3 is the second input node of the optical circuit, and port 4 is the second output node of the optical circuit. The optical monitor is a planar waveguide type optical monitor integrating the first optical coupler, the second optical coupler, the input-side optical multiplexer / demultiplexer, the first asymmetric arm, the second asymmetric arm, the output-side optical multiplexer / demultiplexer, the first light receiver, and the second light receiver. Let the physical length of the optical waveguide in the non-common portion of the first asymmetric arm be (L+ΔL), and the group refractive index be n2. Let the physical length of the optical waveguide in the second asymmetric arm be L, and the group refractive index be n1. Let the linear expansion coefficient of the substrate in the planar waveguide optical monitor be α, satisfying dn1 / dT+n1α>dn2 / dT+n2α. The phase difference θ between the photocurrent from the first photodetector and the photocurrent from the second photodetector is obtained through... To express this, the physical length L is obtained through the following formula in a way that ensures the temperature derivative of the above equation is always 0. 。 12. The optical module according to any one of claims 3 to 5, wherein, The optical module has a temperature regulator that controls the temperature supplied to the semiconductor laser and the optical monitor to change when the wavelength monitoring value Iλ / Ip deviates from the wavelength setting value. The wavelength monitoring value Iλ / Ip is the ratio of the optical power monitoring value Ip, which is the sum of the first monitoring value and the second monitoring value, to the wavelength monitoring value Iλ, which is the difference between the first monitoring value and the second monitoring value. The temperature regulator adjusts the temperature at the semiconductor laser and the temperature at the optical monitor.

13. The optical module according to claim 12, wherein, This optical module has the following features: Support on which the temperature regulator is mounted; The base, which is mounted on the mounting surface of the temperature regulator, has: a vertical portion on which the semiconductor laser is mounted and fixed; and a flat portion integrally formed with the vertical portion, on which the optical monitor is mounted and fixed at a position for receiving the backward laser beam from the semiconductor laser. as well as A cylindrical cover with one open end has a bottom and a side wall portion. The bottom has a window for emitting forward laser light from the semiconductor laser. The cover covers the inner plane of the support. The open end face of the side wall portion is connected to the peripheral end of the inner plane of the support and is fixed thereto.

14. The optical module according to claim 13, wherein, This optical module has the following features: The main signal pin passes through the support and is connected to the electrode of the semiconductor laser at the internal lead portion exposed from the inner plane of the support; The first monitoring pin passes through the bracket and is connected to the first light receiver of the optical monitor at the internal lead portion exposed from the inner plane of the bracket. A second monitoring pin, which passes through the bracket, connects to the second light receiver of the optical monitor at an internal lead portion exposed from the inner plane of the bracket; and A pair of temperature control pins pass through the support and are connected to a pair of electrodes in the temperature regulator at an internal lead portion exposed from the inner plane of the support.

15. The optical module according to any one of claims 3 to 5, wherein, The optical circuit used to construct the interferometric measurement system is a 90-degree hybrid structured optical circuit as follows: It receives light output from the first asymmetric arm at the first input node, receives light output from the second asymmetric arm at the second input node, outputs I-type light at the first output node, and outputs Q-type light at the second output node. The first photodetector receives the I-light output from the 90-degree hybrid structured optical loop and outputs the first monitoring value as the I signal. The second photodetector receives the Q-light output from the 90-degree hybrid structured optical loop and outputs the second monitoring value as the Q signal.

16. The optical module according to claim 15, wherein, The first light receiver has a first I light receiver and a second I light receiver connected in series, and outputs the first monitoring value to the connection point of the first I light receiver and the second I light receiver. The second light receiver has a first Q light receiver and a second Q light receiver connected in series, and outputs the second monitoring value to the connection point of the first Q light receiver and the second Q light receiver. The 90-degree hybrid structured optical circuit has the following characteristics: The first 1×2 optical combiner / demultiplexer has a first port to a third port, the first port being optically connected to the output node of the first asymmetric arm; The second 1×2 optical combiner / demultiplexer has a first port to a third port, the first port being optically connected to the output node of the second asymmetric arm; A 90-degree delay unit, the input node of which is optically connected to the third port of the second 1×2 optical multiplexer / demultiplexer; A first 2×2 optical multiplexer / demultiplexer has ports 1 to 4. Port 1 is optically connected to port 2 of the first 1×2 optical multiplexer / demultiplexer, and port 3 is optically connected to port 2 of the second 1×2 optical multiplexer / demultiplexer. The first I output light from port 3 is output to the first I light receiver, and the second I output light from port 4 is output to the second I light receiver. The second 2×2 optical multiplexer / demultiplexer has ports 1 to 4. Port 1 is optically connected to port 3 of the second 1×2 optical multiplexer / demultiplexer, and port 3 is optically connected to the output node of the 90-degree delay unit. The first Q-wavelength output light from port 3 is output to the first Q-wavelength receiver, and the second Q-wavelength output light from port 4 is output to the second Q-wavelength receiver. The I-light output consists of the first I-light output light and the second I-light output light, and the Q-light output consists of the first Q-light output light and the second Q-light output light.

17. The optical module according to claim 5, wherein, The optical circuit used to construct the interferometric measurement system is a 90-degree hybrid structured optical circuit as follows: It receives light output from the first asymmetric arm at the first input node, receives light output from the second asymmetric arm at the second input node, outputs I-type light at the first output node, and outputs Q-type light at the second output node. The first photodetector receives the I-light output from the 90-degree hybrid structured optical loop and outputs the first monitoring value as the I signal. The second photodetector receives the Q-band light output from the 90-degree hybrid structured optical loop and outputs the second monitoring value as the Q signal. The optical monitor is a planar waveguide type optical monitor integrating the first optical coupler, the second optical coupler, the input-side optical multiplexer / demultiplexer, the first asymmetric arm, the second asymmetric arm, the 90-degree hybrid structured optical loop, the first light receiver, and the second light receiver. Let the physical length of the optical waveguide in the non-common portion of the first asymmetric arm be (L+ΔL), and the group refractive index be n2. Let the physical length of the optical waveguide in the second asymmetric arm be L, and the group refractive index be n1. Let the linear expansion coefficient of the substrate in the planar waveguide optical monitor be α, satisfying dn1 / dT+n1α>dn2 / dT+n2α. The phase difference θ between the photocurrent from the first photodetector and the photocurrent from the second photodetector is obtained through... To express this, the physical length L is obtained through the following formula in a way that ensures the temperature derivative of the above equation is always 0. 。 18. The optical module according to claim 15, wherein, The optical module has a temperature regulator that controls the temperature supplied to the semiconductor laser and the optical monitor to change when the wavelength monitoring value Iλ / Ip deviates from the wavelength set value. The wavelength monitoring value Iλ / Ip is the ratio of the optical power monitoring value Ip obtained by mapping the I signal represented by the first monitoring value and the Q signal represented by the second monitoring value to the trajectory points on the IQ plane, to the wavelength monitoring value Iλ. The temperature regulator adjusts the temperature at the semiconductor laser and the temperature at the optical monitor.

19. The optical module according to claim 15, wherein, The optical module has: A temperature regulator controls the temperature supplied to the semiconductor laser and the optical monitor to change when the wavelength monitoring value Iλ / Ip deviates from the wavelength set value. The wavelength monitoring value Iλ / Ip is the ratio of the optical power monitoring value Ip obtained by mapping the I signal represented by the first monitoring value and the Q signal represented by the second monitoring value to the trajectory points on the IQ plane, to the wavelength monitoring value Iλ. The temperature regulator adjusts the temperature at the semiconductor laser and the temperature at the optical monitor. Support on which the temperature regulator is mounted; The base, which is mounted and fixed on the mounting surface of the temperature regulator, has: a vertical section, which mounts and fixes the semiconductor laser; And a planar portion, which is integrally formed with the vertical portion, and the optical monitor is mounted and fixed at the position where the back laser of the semiconductor laser is received; A cylindrical cover with one open end has a bottom and a side wall portion. The bottom has a window for emitting forward laser light from the semiconductor laser, which covers the inner plane of the support. The open end face of the side wall portion is connected to and fixed to the peripheral end of the inner plane of the support. The main signal pin passes through the support and is connected to the electrode of the semiconductor laser at the internal lead portion exposed from the inner plane of the support; The first monitoring pin passes through the bracket and connects the connection point of the first I light receiver and the second I light receiver at the internal lead portion exposed from the inner plane of the bracket. The second monitoring pin passes through the bracket and connects the connection point of the first Q light receiver and the second Q light receiver at the internal lead portion exposed from the inner plane of the bracket. A pair of temperature control pins, extending through the support, connect to a pair of electrodes in the temperature regulator at an internal lead portion exposed from the inner plane of the support; and The light-receiving section has a power supply pin that connects to the power supply side electrode of the first I light receiver located on the power supply side of the first light receiver and the power supply side electrode of the first Q light receiver located on the power supply side of the second light receiver.

20. A control method for an optical module, wherein, The optical module includes: a semiconductor laser; an optical monitor that receives laser light from the semiconductor laser and outputs a first monitoring value and a second monitoring value for estimating the intensity and wavelength of the laser light from the semiconductor laser; and a temperature regulator that regulates the temperature at the semiconductor laser and the temperature at the optical monitor, wherein the optical monitor includes: a first optical coupler that receives laser light from the semiconductor laser; a second optical coupler that receives laser light from the semiconductor laser; and a first light receiver that outputs the first monitoring value. And a second light receiver, which outputs the second monitoring value, wherein the first path from the first optical coupler to the first light receiver and the second path from the second optical coupler to the second light receiver are asymmetric, wherein, The control method of the optical module includes a temperature adjustment step, in which, when the wavelength monitoring value Iλ / Ip deviates from the wavelength setting value, the temperature regulator adjusts the temperature supplied to the semiconductor laser and the optical monitor. The wavelength monitoring value Iλ / Ip is the ratio of the optical power monitoring value Ip, which is the sum of the first monitoring value and the second monitoring value, and the wavelength monitoring value Iλ, which is the difference between the first monitoring value and the second monitoring value.

Images