Optical Module

Abstract

An optical module according to the present invention includes: a temperature controller (2) that performs a function of adjusting the temperature of a semiconductor laser (5); and an optical monitor (6) that performs a function of monitoring the optical output from the semiconductor laser (5) and monitoring the oscillation wavelength.　The optical module further includes a heater (7) and a thermistor (8) that are housed in a package (1).　The heater (7) and the thermistor (8) are electrically connected in parallel, and one end of the heater (7) and one end of the thermistor (8) are connected to a heater and thermistor-shared lead pin (P7).

Description

[Technical Field]

[0001] The present disclosure relates to optical modules. [Background technology]

[0002] As the capacity of optical communication systems increases, there is a demand for more advanced optical communication modules to be used in optical communication systems. Some increasingly sophisticated optical communication modules require not only the application of current to a semiconductor laser but also many other functions such as a temperature monitor or temperature regulator for temperature control, an optical output monitor or an oscillation wavelength monitor.

[0003] For example, Patent Document 1 discloses a laser (LD) and a device for monitoring the light emitted from the rear end face of the laser. The laser module shown in the figure contains, in a package, a photodetector (PD) that monitors the light emitted from the rear end face of the laser and transmitted through the etalon, a thermistor that detects the temperature of the laser, and first and second Peltier elements, each of which has a terminal for applying current and which are connected in series or in parallel to a pair of input terminals for external signals provided on the module. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-69130 Summary of the Invention [Problem to be solved by the invention]

[0005] In the laser module shown in Patent Document 1, eight terminals for exchanging electrical signals between the inside and outside of the package are shown in an oblique view that more specifically shows the main structure, but the relationship between the terminals and the components housed inside the package is not shown. In addition to the two input terminals for the first and second Peltier elements, judging from the schematic diagram showing the structure, at least six terminals are required: a laser, two light-receiving elements, a terminal for the thermistor, and a ground terminal. On the other hand, there is a demand for optical communication modules to be made more sophisticated by adding more functions to them, and for optical communication modules to be made smaller. The miniaturization of optical communication modules is also limited by the number of terminals that exchange electrical signals between the inside and outside of the package.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and aims to reduce the size of an optical module equipped with a semiconductor laser, which has a heater and a thermistor inside the package. [Means for solving the problem]

[0007] The optical module according to the present disclosure ,vinegarThe package is made up of a stem and a cylindrical windowed cap fixed so that the open end face of the side wall contacts the peripheral end of the inner flat surface of the stem; a semiconductor laser housed in the package and emitting laser light from the window of the windowed cap; an optical monitor housed in the package and receiving the laser light from the semiconductor laser and monitoring the laser light from the semiconductor laser; a temperature regulator housed in the package and controlling the temperature of the semiconductor laser and the temperature of the optical monitor when a monitored value from the optical monitor deviates from a set monitored value, to adjust the temperature of the semiconductor laser and the temperature of the optical monitor; a heater housed in the package; and a thermistor housed in the package and electrically connected in parallel with the heater. a laser lead pin that is electrically insulated from and passes through the stem, and an electrode of a semiconductor laser is connected to an inner lead portion exposed from the inner flat surface of the stem; a monitor lead pin that is electrically insulated from and passes through the stem, and an output end of an optical monitor is connected to the inner lead portion exposed from the inner flat surface of the stem; a temperature regulator lead pin that is electrically insulated from and passes through the stem, and an electrode of a temperature regulator is connected to the inner lead portion exposed from the inner flat surface of the stem; a heater / thermistor common lead pin that is electrically insulated from and passes through the stem, and one end of a heater and one end of a thermistor are connected to the inner lead portion exposed from the inner flat surface of the stem; and a ground lead pin that is electrically connected to the stem. [Effects of the Invention]

[0008] According to the present disclosure, the heater and thermistor housed in the package are electrically connected in parallel, and the lead pins for the heater and thermistor are shared, thereby enabling miniaturization. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a state in which a cap is removed from the optical module according to the first embodiment. FIG. [Figure 2] 1 is a perspective view showing an optical module according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] 1 is a block diagram showing an optical monitor in an optical module according to a first embodiment. [Figure 5] FIG. 2 is a schematic perspective view showing an optical monitor in the optical module according to the first embodiment. [Figure 6] 1 is a schematic block diagram showing an optical module device according to a first embodiment. [Figure 7] 3 is a circuit diagram of a heater and a thermistor in the optical module according to the first embodiment, and a diagram showing the relationship between lead pins. FIG. [Figure 8] 5 is a diagram showing the relationship between the temperature of the thermistor and the parallel resistance value of the heater and the thermistor in the optical module according to the first embodiment. FIG. [Figure 9] 10A and 10B are circuit diagrams of a heater and a thermistor in an optical module according to a reference example, and diagrams showing the relationship between lead pins. [Figure 10] FIG. 10 is a diagram showing the resistance value versus the temperature of a heater in an optical module according to a reference example. [Figure 11] FIG. 10 is a diagram showing the relationship between the temperature and resistance value of a thermistor in the optical module according to the reference example. [Figure 12] 10 is a circuit diagram of a heater and a thermistor in an optical module according to a second embodiment, and a diagram showing the relationship between lead pins. FIG. [Figure 13] 10 is a circuit diagram of a heater and a thermistor in a modified example of the optical module according to the second embodiment, and a diagram showing the relationship between lead pins. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 The optical module according to the first embodiment will be described with reference to FIGS. The optical module according to the first embodiment is suitable for use as a light source module for digital coherent communication. The optical module according to the first embodiment is an example applied to a TO-CAN type optical transmission module for optical communications.

[0011] The optical module according to the first embodiment is an optical module equipped with a single-wavelength semiconductor laser. The optical module according to the first embodiment is an optical module having a function of adjusting the temperature of a semiconductor laser, and a function of monitoring the optical output and oscillation wavelength from the semiconductor laser. Therefore, the following description will be given taking as an example a TO-CAN type optical transmission module for optical communications that includes a single-wavelength semiconductor laser.

[0012] As shown in FIGS. 1 to 3, the optical module according to the first embodiment includes a package 1 including a stem 11 and a cap 12 with a window (hereinafter referred to as a cap), and a temperature regulator 2. and , pedestal 3 and , a semiconductor laser submount (hereinafter referred to as a submount) 4 and , semiconductor laser 5 and , Optical Monitor 6 and The heater 7, the thermistor 8, a plurality of lead pins P2 to P7, and a ground lead pin P1 are provided. 1 and 3, in order to avoid complexity, wires electrically connecting the components 2, 5, 6, 7, and 8 to the lead pins P1 to P6 are omitted.

[0013] The stem 11 is made of a metal disk. The shape of the stem 11 is not limited to a disk, but may be a cylindrical or rectangular prism, or may be a flat plate having an inner flat surface 11a and an outer flat surface 11b parallel to the inner flat surface 11a. The inner flat surface 11a of the stem 11 is the mounting surface, which is the area for mounting components. In this example, the stem 11 is a metal disk having a diameter of 5.6 mm.

[0014] The cap 12 is a cylindrical lens cap made of metal, with one end open, a bottom portion, and a side wall portion, and an outer diameter slightly smaller than the diameter of the stem 11 . An opening is formed in the center of the bottom of the cap 12, which is a window 13, in which a flat glass or lens is mounted. The window 13, which is a flat glass or lens, is attached by bonding with an adhesive or by melting in an opening formed in the bottom portion so that airtightness is maintained inside and outside the cap.

[0015] The end face of the side wall of the cap 12 is in contact with the peripheral end of the inner flat surface 11a of the stem 11 and is joined and fixed by electric welding. The interior enclosed by the stem 11 and the cap 12 is filled with an inert gas or is in a vacuum state, and the semiconductor laser 5 is isolated from the outside air and hermetically sealed. From the window 13, the semiconductor laser 5 emits a forward laser beam Lf. The stem 11 and the cap 12 form a TO-CAN type package.

[0016] The temperature regulator 2 is housed in a package and placed on the stem 11 . The temperature controller 2 has a flat lower surface 2a and a flat upper surface 2b parallel to the lower surface 2a, and the lower surface 2a is fixed to the inner flat surface 11a of the stem 11 with solder or a conductive adhesive, and the upper surface 2b serves as the mounting surface. Hereinafter, the upper surface 2b will be referred to as the mounting surface. The temperature regulator 2 heats or cools the mounting surface 2b by passing a current through it.

[0017] When the monitor value from the optical monitor 6 deviates from the set monitor value, the temperature regulator 2 performs control to change the temperature applied to the semiconductor laser 5 and the optical monitor 6. That is, the temperature regulator 2 regulates the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 . The temperature controller 2 is a thermoelectric cooler (TEC) configured with a Peltier element.

[0018] The base 3 is placed on the mounting surface 2b of the temperature controller 2 and is an L-shaped metal member having a flat portion 3a with flat upper and lower surfaces and an upright portion 3b formed integrally with the flat portion 3a with a flat vertical surface, and a step portion having a horizontal mounting surface 3c on the opposite side of the upright surface of the upright portion 3b. The lower surface of the flat portion 3a of the base 3 is fixed to the mounting surface 2b of the temperature controller 2 with solder or a conductive adhesive.

[0019] A semiconductor laser 5 is mounted and fixed on the vertical surface of the vertical surface portion 3b of the base 3 via a submount 4 for the semiconductor laser. The semiconductor laser 5 is fixed to the vertical surface of the vertical portion 3 b of the base 3 so that the optical axis of the forward laser light Lf and the optical axis of the backward laser light Lb of the semiconductor laser 5 coincide with the central axis of the stem 11 . The submount 4 is configured by a base made of a dielectric material such as aluminum nitride (AlN) on the surface of which a metal wiring layer is patterned.

[0020] An optical monitor 6 is placed and fixed on the upper surface of the flat portion 3 a of the base 3 . The optical monitor 6 is fixed to the upper surface of the flat portion 3 a of the base 3 so as to receive the rear laser light Lb from the semiconductor laser 5 . The optical monitor 6 is disposed at an angle that allows it to receive the rear laser light Lb from the semiconductor laser 5 . For example, if the angle at which the maximum coupling efficiency of the optical coupler 61 (see Figures 4 and 5) in the optical monitor 6 for the backward laser light Lb of the semiconductor laser 5 is obtained is 90 degrees relative to the plane 6a of the optical monitor 6, then the optical monitor 6 is positioned at a 90-degree angle; if the angle is 80 degrees, then the optical monitor 6 is positioned at a 80-degree angle.

[0021] When the angle of the optical monitor 6 with respect to the backward laser light Lb of the semiconductor laser 5 is set to 90 degrees, the angle formed by the upper surface of the flat portion 3a of the base 3 and the vertical surface of the vertical portion 3b of the base 3 is set to 90 degrees. Furthermore, when the angle of the optical monitor 6 relative to the rear laser light Lb of the semiconductor laser 5 is set to 80 degrees, the upper surface of the flat portion 3a of the base 3 may be inclined, and the angle between the upper surface of the flat portion 3a of the base 3 and the vertical surface of the vertical portion 3b of the base 3 may be set to 80 degrees.

[0022] In the first embodiment, the semiconductor laser 5 is mounted and fixed on the vertical portion 3b of the base 3, and the optical monitor 6 is mounted and fixed on the flat portion 3a of the base 3. However, the semiconductor laser 5 and the optical monitor 6 may be housed inside the package 1, and may be arranged in such a manner that the forward laser light Lf of the semiconductor laser 5 is emitted to the outside of the package 1, and the backward laser light Lb of the semiconductor laser 5 is received by the optical monitor 6.

[0023] The thermistor 8 is placed and fixed on the placement surface 3c of the stepped portion of the base 3. The base 3 conducts heat from the mounting surface 2 b of the temperature regulator 2 through the submount 4 to regulate the temperature of the semiconductor laser 5 , that is, heats or cools the semiconductor laser 5 . At the same time, the base 3 conducts heat from the mounting surface 2 b of the temperature regulator 2 to adjust the temperature of the optical monitor 6 , that is, heats or cools the optical monitor 6 . The semiconductor laser 5 and optical monitor 6, whose temperature is controlled by the temperature controller 2, are arranged vertically on the base 3, so that the area occupied by the semiconductor laser 5 and optical monitor 6 on the mounting surface 2b of the temperature controller 2 can be reduced, resulting in a reduction in the size of the temperature controller 2 and the optical module.

[0024] A thermistor 8 is housed in the package 1 to measure the temperature inside the package 1 . The thermistor 8 is housed in the package 1 to perform temperature control by the temperature regulator 2 with high precision and to improve the functionality of the optical module. That is, in advance of preparation for operating the optical module, by detecting the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 using the thermistor 8, it is possible to know with higher accuracy the relationship between the target value of the monitor value based on the laser light from the semiconductor laser 5 and the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6.

[0025] Furthermore, by detecting the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 using the thermistor 8 periodically, periodically, or randomly during operation of the optical module, the temperatures of the semiconductor laser 5 and the optical monitor 6 during operation of the optical module can be known with higher accuracy.

[0026] In this example, the thermistor 8 is mounted and fixed on the mounting surface 3c of the stepped portion of the pedestal 3, and therefore can measure and detect the temperature of the pedestal 3, that is, the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6. Although the thermistor 8 is mounted and fixed on the mounting surface 3c of the stepped portion of the base 3, it may also be mounted and fixed on a portion other than the mounting surface 3c of the stepped portion of the base 3, on the mounting surface 2b of the temperature regulator 2, or on the inner flat surface 11a of the stem 11. In short, it is only necessary that the thermistor 8 is housed in the package 1, measures the temperature inside the package 1, and detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 from the measurement result.

[0027] The semiconductor laser 5 is a single-wavelength semiconductor laser, i.e., a single-mode laser that oscillates at a single wavelength. As the 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. The semiconductor laser 5 emits a forward laser beam Lf from the emission surface and a backward laser beam Lb from the rear surface. The forward laser beam Lf is used for optical communication, and the backward laser beam Lb is monitored.

[0028] In this type of single-wavelength semiconductor laser, the light intensity varies depending on the drive current supplied, and also varies depending on the temperature of the laser itself; generally, the lower the temperature, the greater the light output. Furthermore, the wavelength of the laser light emitted from a single-wavelength semiconductor laser varies depending on the temperature of the laser and Joule heat generated by the drive current. Therefore, in embodiment 1, the backward laser light 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 light emitted from the semiconductor laser 5 constant.

[0029] The optical monitor 6 outputs a monitor value for causing the temperature regulator 2 to control the temperature applied to the semiconductor laser 5 and the optical monitor 6 to a control unit 9 (see FIG. 6) that controls the temperature regulator 2. The control unit 9 controls the temperature regulator 2, the semiconductor laser 5, the optical monitor 6, and the heater 7. The control unit 9 exchanges signals with each of the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2, and controls the current and voltage to each of the semiconductor laser 5, the optical monitor 6, and the temperature regulator 2, thereby controlling the light intensity and wavelength of the laser light from the semiconductor laser 5. Temperature information obtained by the thermistor 8 is input to the control unit 9 in advance preparation, and temperature information obtained by the thermistor 8 is input to the control unit 9 periodically, periodically, or randomly during operation of the optical module.

[0030] The optical monitor 6 measures the light intensity of the backward laser light Lb from the semiconductor laser 5, and obtains an optical power monitor value Ip, which is one of the monitor values ​​consisting of a current value for controlling the value of the drive current to the semiconductor laser 5 so that the optical output of the semiconductor laser 5 becomes a target value, and also obtains a wavelength monitor value Iλ, which is one of the monitor values ​​consisting of a current value used to control the value of the current supplied to the temperature regulator 2 so that the wavelength of the laser light from the semiconductor laser 5 becomes a target value. The optical monitor 6 constitutes a part of a wavelength locker for controlling the wavelength of the laser light from the semiconductor laser 5 .

[0031] When the optical power monitor value Ip is larger than a current setting value, which is one of the set monitor values, the temperature regulator 2 heats the mounting surface 2b in accordance with the value of the supplied current to increase the temperature applied to the semiconductor laser 5 and the optical monitor 6, and when the optical power monitor value Ip is smaller than the current setting value, the temperature regulator 2 cools the mounting surface 2b in accordance with the value of the supplied current to decrease the temperature applied to the semiconductor laser 5 and the optical monitor 6, under control of the control unit 9. The current setting value is set, for example, to ±10% of the target value Ip_target of the optical power monitor value Ip when a drive current that sets the optical output of the semiconductor laser 5, i.e., the optical intensity, to the target value is supplied to the semiconductor laser 5.

[0032] When the wavelength monitor value Iλ / Ip, which is the ratio between the optical power monitor value Ip and the wavelength monitor value Iλ, deviates from the wavelength set value, which is one of the set monitor values, the temperature regulator 2 changes the temperature of the mounting surface 2b in accordance with the value of the supplied current, thereby changing the temperature applied to the semiconductor laser 5 and the optical monitor 6. In this example, when the wavelength monitor value Iλ / Ip is larger than the wavelength setting value, the temperature regulator 2 heats the mounting surface 2b in accordance with the value of the supplied current, thereby increasing the temperature applied to the semiconductor laser 5 and the optical monitor 6; and when the wavelength monitor value Iλ / Ip is smaller than the wavelength setting value, the temperature regulator 2 cools the mounting surface 2b in accordance with the value of the supplied current, thereby decreasing the temperature applied to the semiconductor laser 5 and the optical monitor 6. The wavelength set value is set, for example, to ±10% of the target value Iλ_target of the wavelength monitor value Iλ / Ip when the wavelength λLD of the laser light from the semiconductor laser 5 is set to the target value λ_target.

[0033] As shown in FIGS. 4 and 5, the optical monitor 6 includes an optical coupler 61, a demultiplexer 62, a first optical receiver 63, an optical filter 64, a second optical receiver 65, and optical waveguides 661-665. The optical monitor 6 is, for example, a planar waveguide type optical monitor using a silicon photonics chip formed by integrating an optical coupler 61, a splitter 62, a first optical receiver 63, an optical filter 64, a second optical receiver 65, and optical waveguides 661 to 665 on the plane of a silicon (Si) substrate 6A. The optical waveguides 661 to 665 are silicon waveguides made of silicon.

[0034] The optical coupler 61 receives the backward laser light Lb from the semiconductor laser 5 and couples the backward laser light Lb, which is incident perpendicularly to the flat surface 6 a of the optical monitor 6 , into the optical waveguide 661 . The optical coupler 61 is, for example, a grating coupler. The grating coupler has the function of coupling the backward laser light Lb from the semiconductor laser 5 coming from above the flat surface 6a of the optical monitor 6 to the optical waveguide 661, so the flat surface 6a of the optical monitor 6 and the semiconductor laser 5 are positioned by the base 3 at an angle that provides the maximum coupling efficiency of the grating coupler. The optical coupler 61 may be an elephant coupler. A grating coupler is preferable for the optical coupler 61 of this example because it can widen the optical mode and has the advantage of being less position-dependent than end face coupling of a waveguide.

[0035] The demultiplexer 62 demultiplexes the backward laser light Lb from the semiconductor laser 5 received by the optical coupler 61 and transmitted via the optical waveguide 661 into two laser lights. The demultiplexer 62 is, for example, a directional coupler, a multi-mode interferometer (MMI), or a Y-branch waveguide. In this example, the demultiplexer 62 is an MMI.

[0036] The first photoreceiver 63 receives the backward laser light Lb from the semiconductor laser 5 via the optical coupler 61, and receives one of the laser lights branched from the branching filter 62 via the optical waveguide 662, performs photoelectric conversion on the received light, and outputs a current corresponding to the backward laser light Lb from the semiconductor laser 5 to the output terminal as a first monitor value. The first photodetector 63 functions as an optical power monitor for the semiconductor laser 5 because it converts the backward laser light Lb from the semiconductor laser 5 coupled by the optical coupler 61 directly into a current.

[0037] That is, the current value Ip of the current obtained from the first photoreceiver 63 is the optical power monitor value Ip that indicates the optical output of the laser light from the semiconductor laser 5, i.e., the optical intensity, by the current value, and the first photoreceiver 63 outputs the optical power monitor value Ip to the output terminal as the first monitor value. The first light receiver 63 is a waveguide type light receiver or a surface incident type light receiver, and in this example, a photodiode that is a SiGe (silicon germanium) light receiver is used.

[0038] The optical filter 64 receives the backward laser light Lb from the semiconductor laser 5 via the optical coupler 61 and the other laser light branched by the branching filter 62 via the optical waveguide 663 . The optical filter 64 is a variable phase optical filter having wavelength temperature dependency. That is, the peak value of the wavelength of the laser light output from the optical filter 64 has temperature dependency such that it shifts to the longer wavelength side as the temperature of the optical filter 64 increases.

[0039] The optical filter 64 is a ring resonator, and in this example, the ring resonator is used as a filter having periodic characteristics. The optical filter 64 is not limited to a ring resonator filter. The optical filter 64 is ideally a filter that does not have temperature dependency. However, in general, the temperature dependency is difficult to make zero, and a filter having temperature dependency that shifts to the long wavelength side as the temperature increases, or a filter having temperature dependency that shifts to the short wavelength side as the temperature increases, may also be used.

[0040] Instead of a ring resonator filter, a Mach-Zehnder interferometer (MZ interferometer) or a distributed Bragg reflector (DBR) filter may be used. In this example, a ring resonator 64a is used as the optical filter 64, and hereinafter the ring resonator 64a will be referred to as a ring resonator filter.

[0041] The ring resonator filter 64a is composed of an optical waveguide that forms a closed loop. The optical waveguide 663 connected to the other output end of the demultiplexer 62 is the input side, and the optical waveguide 664 connected to the input end of the second photodetector 65 is the output side. The optical waveguides forming a closed loop that constitute the ring resonator filter 64a are coupled to the input side optical waveguide 663 and the output side optical waveguide 664 that is continuous with the optical waveguide 663, causing resonance within the closed loop optical waveguide, and the ring resonator filter 64a functions as a filter.

[0042] The ring resonator filter is also coupled to another output-side optical waveguide 665 arranged opposite to the output-side optical waveguide 664 with respect to the ring resonator filter 64a. The optical waveguide forming a closed loop that constitutes the ring resonator filter 64a is a silicon waveguide made of silicon. The optical waveguide forming the closed loop has a diameter of about 100 μm, which is very small and allows for miniaturization, and also makes it possible to suppress the influence of temperature gradients due to the environmental temperature of the ring resonator filter 64a.

[0043] As the second photodetector 65, either a photodiode 65a that is connected to, i.e., coupled to, the ring resonator filter 64a via an output-side optical waveguide 664 and receives transmitted light from the ring resonator filter 64a, or a photodiode 65b that is connected to, i.e., coupled to, the ring resonator filter 64a via another output-side optical waveguide 665 arranged opposite the optical waveguide 664 and receives transmitted light from the ring resonator filter 64a, is used.

[0044] As is generally known, the output side optical waveguide 664 and the other output side optical waveguide 665 are arranged opposite to each other with respect to the ring resonator filter 64a, and therefore the intensity versus phase of the current flowing through the photodiode 65a connected to the through port of the output side optical waveguide 664 exhibits characteristics that are inverted from the intensity versus phase of the current flowing through the photodiode 65b connected to the drop port of the other output side optical waveguide 665.

[0045] That is, the intensity relative to the phase of the current flowing through each of the photodiodes 65a and 65b inverts from 1 to 0 and from 0 to 1 every 2π, and when the intensity relative to the phase of the current flowing through one photodiode 65a indicates 1, the intensity relative to the phase of the current flowing through the other photodiode 65b indicates 0. Conversely, when the intensity relative to the phase of the current flowing through one photodiode 65a indicates 0, the intensity relative to the phase of the current flowing through the other photodiode 65b indicates 1.

[0046] In short, the gradient of the intensity of the current flowing through the photodiode 65a is similar to the gradient of the intensity of the current flowing through the photodiode 65b. Therefore, it is sufficient to use either the photodiode 65a or the photodiode 65b as the second light receiver 65.

[0047] The output from the second photodetector 65 is laser light that is received, i.e., coupled, by the optical coupler 61, and the other laser light that is branched off from the branching filter 62 is filtered by the ring resonator filter 64a, which is the phase-variable optical filter 64. In this example, the laser light that resonates with the backward laser light Lb is converted into current, so that when the wavelength of the backward laser light Lb changes, the current value from the second photodetector 65 also changes according to the wavelength dependency of the ring resonator filter 64a.

[0048] Therefore, the current value Iλ of the current obtained from the second photodetector 65 can be used as the wavelength monitor value Iλ used to obtain the wavelength monitor value Iλ / Ip of the semiconductor laser 5, and the ring resonator filter 64a and the second photodetector 65 function as a wavelength monitor for the semiconductor laser 5. The current value Iλ of the current obtained from the second photoreceiver 65 is the wavelength monitor value Iλ, and the second photoreceiver 65 outputs the optical power monitor value Ip as the second monitor value to the output terminal.

[0049] The wavelength monitor value Iλ, that is, the current value Iλ obtained from the second light receiver 65, changes not only with the wavelength of the backward laser light Lb of the semiconductor laser 5 but also with the light intensity of the backward laser light Lb. Therefore, by dividing the wavelength monitor value Iλ by the optical power monitor value Ip, the wavelength monitor value Iλ / Ip based only on the wavelength of the backward laser light Lb can be obtained.

[0050] Since the temperatures of the semiconductor laser 5 and the optical monitor 6 are adjusted by the heat from the mounting surface 2b of the temperature regulator 2 via the base 3, the temperature rise in the semiconductor laser 5 and the temperature rise in the optical monitor 6 are the same. If the temperature of the optical monitor 6 changes, the wavelength monitor value Iλ / Ip exhibits a straightforward wavelength dependency. In this example, as the temperature increases relative to the wavelength of the laser light from the semiconductor laser 5, the wavelength monitor value Iλ / Ip has a downward slope. By adjusting the temperature of the semiconductor laser 5, the wavelength of the laser light of the semiconductor laser 5 can be adjusted, and precise control can be performed on the single wavelength of the laser light of the semiconductor laser 5.

[0051] In this example, the optical filter 64 further includes a phase modulator 64b disposed on the optical waveguide forming a closed loop that constitutes the ring resonator filter 64a. The phase modulator 64b is a heater 7 in this example. The position of the peak wavelength λfilt of the ring resonator filter 64a, that is, the position of the peak of the current value Iλ obtained from the second photodetector 65, generally varies between individual ring resonator filters 64a due to manufacturing errors.

[0052] The phase modulator 64b controls the ring resonator filter 64a, that is, adjusts the position of the peak wavelength λfilt produced by the ring resonator filter 64a. The current supplied to the heater 7, which is the phase modulator 64b, is the target value Ih_target of the current to be supplied to the heater 7, which will obtain the peak wavelength λfilt in the ring resonator filter 64a when the semiconductor laser 5 outputs an optical output in which the wavelength λLD is the target value λ_target and the optical intensity is the target value Ip_target of the optical power monitor value Ip, as obtained in the preliminary preparations for operating the optical module.

[0053] That is, in order to obtain the current value Iλ obtained from the second photodetector 65 to obtain the target value Iλ_target of the wavelength monitor value Iλ / Ip relative to the target value λ_target of the wavelength λLD of the laser light from the semiconductor laser 5, the position of the peak wavelength λfilt by the ring resonator filter 64a is adjusted by the phase modulator 64b. For example, if the target value Iλ_target is at a position where the wavelength monitor value Iλ / Ip=0, even if the wavelength λLD of the laser light from the semiconductor laser 5 changes, there will be almost no change in the wavelength monitor value Iλ / Ip, and the ring resonator filter 64a will not be able to be controlled properly. To avoid this, the temperature of the ring resonator filter 64a is adjusted by heating the ring resonator filter 64a with the heater 7, which serves as the phase modulator 64b, so that the target value Iλ_target becomes the wavelength monitor value Iλ / Ip suitable for control.

[0054] The target value Iλ_target suitable for controlling the ring resonator filter 64a is determined by adjusting the temperature of the ring resonator filter 64a using the phase modulator 64b so that it becomes a wavelength monitor value Iλ / Ip near the median value in the region where the slope of the wavelength dependency is large with respect to the temperature of the optical monitor 6, in other words, the temperature of the ring resonator filter 64a.

[0055] The optical monitor 6 need not be a planar waveguide type optical monitor using a silicon photonics chip, but may be a planar waveguide type optical monitor in which an optical coupler 61, a demultiplexer 62, a first optical receiver 63, an optical filter 64, a second optical receiver 65, and optical waveguides 661 to 665 are integrated on the plane of an indium phosphide (InP) substrate 6A, which is a compound semiconductor. The optical monitor 6 may also be a planar waveguide type optical monitor in which an optical coupler 61, a splitter 62, a first optical receiver 63, an optical filter 64, a second optical receiver 65, and optical waveguides 661 to 665 are integrated on the plane of a substrate 6A made of a glass material.

[0056] The optical coupler 61, the splitter 62, the first optical receiver 63, the optical filter 64, the second optical receiver 65, and the optical waveguides 661 to 665 do not necessarily have to be integrated, and individual components may be modularized. The first photoreceiver 63 and the second photoreceiver 65 may be InP photoreceivers.

[0057] The heater 7 serving as the phase modulator 64b is disposed on the upper surface of the optical monitor 6 via a heat insulating layer 6B. In this example, the heat insulating layer 6B is a silicon oxide (SiO2) layer formed on the substrate 6A of the optical monitor 6 so as to cover the optical coupler 61, the splitter 62, the first optical receiver 63, the optical filter 64, the second optical receiver 65, and the optical waveguides 661 to 665. If the optical monitor 6 has sufficient heat insulation properties, the amount of heat generated by the heater 7 is small, and the effect on the thermistor 8 is small, the heat insulating layer 6B may be omitted.

[0058] The heater 7 is arranged on the upper surface of the optical monitor 6, but it may be arranged on the base 3, the mounting surface 2b of the temperature controller 2, or the inner flat surface 11a of the stem 11. In short, in this example, the heater 7 is housed within the package 1, heats the inside of the package 1, has little effect on the thermistor 8, and can directly or indirectly adjust the temperature of the ring resonator filter 64a in the optical monitor 6.

[0059] The temperature regulator 2, the semiconductor laser 5, the optical monitor 6, and the heater 7 are controlled by a control unit 9, as shown in FIG. In preparation for operating the optical module, the control unit 9 receives temperature information from the thermistor 8, i.e., detection information on the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, and during operation of the optical module, the control unit 9 receives detection information on the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 periodically, cyclically, or randomly.

[0060] The control unit 9 inputs the optical power monitor value Ip from the first photodetector 63 of the optical monitor 6 to the semiconductor laser 5, and controls the drive current to the semiconductor laser 5 so that the optical power monitor value Ip falls within a range of ±10% of the target value Ip_target of the optical power monitor value, which is the current setting value.

[0061] The control unit 9 controls the current supplied to the temperature regulator 2 so that the optical power monitor value Ip from the first optical receiver 63 of the optical monitor 6 falls within a current setting value range of ±10% of the target value Ip_target of the optical power monitor value. If the optical power monitor value Ip is greater than the current setting value, the control unit 9 supplies a current to the temperature controller 2 for heating the mounting surface 2b of the temperature controller 2, and if the optical power monitor value Ip is smaller than the current setting value, the control unit 9 supplies a current to the temperature controller 2 for cooling the mounting surface 2b of the temperature controller 2.

[0062] As a result, the temperature regulator 2 controls so as to increase the temperature applied to the semiconductor laser 5 and the optical monitor 6 when the optical power monitor value Ip indicated by the current obtained by the first photodetector 63 is greater than the current setting value, and to decrease the temperature applied to the semiconductor laser 5 and the optical monitor 6 when the optical power monitor value Ip is smaller than the current setting value.

[0063] The control unit 9 also receives input of the optical power monitor value Ip from the first optical receiver 63 of the optical monitor 6 and the wavelength monitor value Iλ from the second optical receiver 65 of the optical monitor 6, calculates the wavelength monitor value Iλ / Ip from the input optical power monitor value Ip and wavelength monitor value Iλ, and controls the current supplied to the temperature regulator 2 so that the wavelength monitor value Iλ / Ip falls within a wavelength setting value range of ±10% of the target value Iλ_target of the wavelength monitor value Iλ / Ip when the wavelength λLD of the laser light from the semiconductor laser 5 is set to the target value λ_target.

[0064] When the wavelength monitor value Iλ / Ip deviates from the wavelength setting value, the control unit 9 supplies a current to the temperature adjuster 2 to change the temperature of the mounting surface 2b. In this example, when the wavelength monitor value Iλ / Ip is greater than the wavelength set value, the control unit 9 supplies a current to the temperature controller 2 for heating the mounting surface 2b of the temperature controller 2, and when the wavelength monitor value Iλ / Ip is smaller than the wavelength set value, the control unit 9 supplies a current to the temperature controller 2 for cooling the mounting surface 2b of the temperature controller 2.

[0065] As a result, the temperature regulator 2 controls so as to increase the temperature applied to the semiconductor laser 5 and the optical monitor 6 when the wavelength monitor value Iλ / Ip, which is determined by the optical power monitor value Ip indicated by the current obtained by the first optical receiver 63 and the wavelength monitor value Iλ indicated by the current obtained by the second optical receiver 65, is greater than the wavelength set value, and to decrease the temperature applied to the semiconductor laser 5 and the optical monitor 6 when the wavelength monitor value Iλ / Ip is smaller than the wavelength set value.

[0066] In addition, the temperature controller 2 detects whether the wavelength monitor value Iλ / Ip is greater than the wavelength setting value. 、 By increasing the temperature applied to the semiconductor laser 5 and the optical monitor 6, when the optical power monitor value Ip becomes smaller than the current setting value, the drive current supplied to the semiconductor laser 5 is increased, and the wavelength monitor value Iλ / Ip becomes smaller than the wavelength setting value. 、 By lowering the temperature applied to the semiconductor laser 5 and the optical monitor 6, the drive current supplied to the semiconductor laser 5 is reduced when the optical power monitor value Ip becomes larger than the current setting value. to make Control is performed.

[0067] The control unit 9 supplies a current of a target value Ih_target to the heater 7, which serves as a phase modulator 64b for the optical filter 64, when the optical intensity of the laser light from the semiconductor laser 5 reaches the target value and the optical output of the laser light whose wavelength λLD of the laser light from the semiconductor laser 5 reaches the target value λ_target is obtained. As a result, under the control of the control unit 9, the heater 7 heats the optical monitor 6, specifically the ring resonator filter 64a, and adjusts the temperature of the ring resonator filter 64a. The control unit 9 and the optical monitor 6 constitute a wavelength locker for controlling the wavelength of the laser light from the semiconductor laser 5 . The optical module and the control unit 9 constitute an optical module device.

[0068] The semiconductor laser 5, optical monitor 6, temperature regulator 2, heater 7, and thermistor 8 are electrically connected to lead pins P1 to P6 by wires (not shown) such as gold wires by wire bonding in order to exchange signals with the control unit 9. The lead pins P1 to P6 pass through respective through holes formed at set positions in the stem 11, and are fixed to the stem 11 by sealing glass that is filled and solidified between the lead pins P1 to P6 and the through holes. The sealing glass electrically insulates the lead pins P1 to P6 from the stem 11, and maintains airtightness.

[0069] One end face of the ground lead pin P7 is in contact with the outer flat surface 11b of the stem 11 and joined by electric welding or brazing, so that the ground lead pin P7 is fixed to the stem 11. The ground lead pin P7 is electrically grounded, and the stem 11 is set to the ground potential by the ground lead pin P7, that is, the stem 11 also serves as a ground node.

[0070] The optical module according to the first embodiment requires a total of seven lead pins, six lead pins P1 to P6 for each component and one ground lead pin P7, and the optical module can be configured with a small number of lead pins. As a result, it is possible to use a standard CAN package with a diameter of 5.6 mm, which has a limit of seven lead pins, thereby achieving miniaturization.

[0071] The connection of the inner lead portions of the lead pins P1 to P6 exposed from the inner flat surface 11a of the stem 11 is, for example, as follows: However, the relationship between the lead pins P1 to P6 and each component is shown as an example and is not limited to this. The lead pin P1 is connected to one electrode of the semiconductor laser 5 and transmits a drive current from the control unit 9 to the semiconductor laser 5. The lead pin P1 is a laser lead pin for the semiconductor laser 5.

[0072] The lead pins P2 and P3 are connected to a pair of electrodes, i.e., a positive electrode and a negative electrode, of the temperature regulator 2, and transmit a current supplied from the control unit 9 to the temperature regulator 2. The lead pins P2 and P3 are temperature regulator lead pins for the temperature regulator 2. The lead pins P4 and P5 are connected to the output terminals of the optical monitor 6 and transmit the monitored values ​​from the optical monitor 6 to the control unit 9. The lead pins P4 and P5 are monitor lead pins for the optical monitor 6.

[0073] The lead pin P4 is connected to the output terminal of the first optical receiver 63 of the optical monitor 6, and transmits a current indicating the optical power monitor value Ip from the first optical receiver 63 to the control unit 9. The lead pin P5 is connected to the output terminal of the second photoreceiver 65 of the optical monitor 6, and transmits a current indicating the wavelength monitor value Iλ from the second photoreceiver 65 to the control unit 9.

[0074] The lead pin P6 is a common lead pin for both the heater and thermistor, to which one end of the heater 7 and one end of the thermistor 8 are connected. The other end of the heater 7 and the other end of the thermistor 8 are electrically connected to the inner flat surface 11a of the stem 11, which is at ground potential (ground node), by wire bonding such as gold wire (not shown), and are connected to the ground lead pin P7.

[0075] That is, as shown in FIG. 7, the heater 7 and thermistor 8 are connected in parallel between the heater / thermistor common lead pin P6 and the ground lead pin P7. For the two components, the thermistor 8 and the heater 7, one common lead pin P6 for both the heater and thermistor is sufficient, excluding the ground lead pin P7, thus reducing the number of lead pins by one.

[0076] Next, the relationship between the thermistor 8, which is one feature of the optical module according to the first embodiment, and the lead pin associated therewith, that is, the lead pin P6 shared by the heater and thermistor, will be described. As described above, the heater 7 functions as a phase modulator 64b for the ring resonator filter 64a in the optical filter 64, and heats the ring resonator filter 64a to adjust the temperature of the ring resonator filter 64a. The heater 7 is low power and has a resistance value R h is high. As described above, the thermistor 8 measures the temperature inside the package 1, and in particular measures and detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, in order to perform temperature control by the temperature regulator 2 with high precision.

[0077] Therefore, it is necessary that the heater 7 and thermistor 8 are controlled independently and that the influence of heating by the heater 7 on thermistor 8 is small. This point will be explained below. The optical module according to the first embodiment has a heater 7 and a thermistor 8 electrically connected in parallel between a heater / thermistor common lead pin P6 and a ground lead pin P7 (ground node), and uses the heater 7 and thermistor 8 shown below as reference examples.

[0078] In this example, the heater 7 has the characteristics of a resistor, and as shown in FIG. 9 as a reference example, the heater 7 shares the ground lead pin P7 with the thermistor 8, but the resistance value R hAs shown in FIG. 10, the resistance shows a constant value of 0.5 kΩ in the temperature range from 0 to 100 degrees. That is, in this example, the heater 7 has a temperature-independent resistance R h is a 0.5 kΩ heater, low power and high resistance. In FIG. 10, the horizontal axis represents the operating temperature of the optical module, which in this example corresponds to the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, and the vertical axis represents the resistance value R of the heater 7. h Shows.

[0079] In this example, the thermistor 8 changes its resistance value R TH As shown in FIG. 9 as a reference example, the resistance R TH As shown in FIG. 11, the resistance value of thermistor 8 decreases as the temperature of thermistor 8 increases, and is 35 kΩ at 0 degrees, 10 kΩ at 25 degrees, 4.16 kΩ at 50 degrees, and 0.7 kΩ at 100 degrees.

[0080] In FIG. 11, the horizontal axis represents the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, and the vertical axis represents the resistance R of the thermistor 8. TH Shows. In this example, the thermistor 8 used had the following characteristics: R0: 10 kΩ, T0: 25 degrees, B constant: 3930K. The curve of the resistance value of thermistor 8 against temperature shown in FIG. 9 shows that the resistance value R0 is 10 kΩ when the temperature T0 is 25 degrees, and the resistance value R0 of a commonly known thermistor at temperature T for a thermistor with a B constant of 3930 K is TH This is the result obtained using the calculation method.

[0081] That is, in the operating temperature range of the optical module according to the first embodiment, the resistance value R TH is the resistance value R of heater 7 h The resistance R of thermistor 8 is larger than TH and the resistance value R of heater 7 h is designed to be close to the value. Specifically, the resistance value R of the heater 7 h shows a constant value independent of temperature, and the resistance value R of thermistor 8 TH changes depending on the temperature, and the resistance R of the thermistor 8 TH and the resistance value R of heater 7 h The relationship is expressed as follows: the resistance value R of the thermistor 8 in the operating temperature range of the semiconductor laser 5 and the optical monitor 6 TH is the resistance value R of heater 7 h The resistance value R of the heater 7 is larger than h It is set to 70 times or less.

[0082] In the optical module according to the first embodiment, the heater 7 and thermistor 8 are electrically connected in parallel between the heater / thermistor common lead pin P6 and the ground lead pin P7. When a DC voltage is applied between the heater / thermistor common lead pin P6 and the ground lead pin P7 to pass a DC current through the heater 7 and thermistor 8, the thermistor 8 has a resistance value R TH changes depending on the temperature, so the resistance value R can be calculated by measuring the voltage between the lead pin P6 shared by the heater and thermistor and the ground lead pin P7. TH By reading the change in the temperature, the temperature inside the package 1, that is, the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, can be measured and detected.

[0083] That is, the parallel resistance R of the heater 7 and the thermistor 8 between the heater / thermistor common lead pin P6 and the ground lead pin P7 is h / / R TH As shown in FIG. 8, the resistance of the thermistor 8 decreases as the temperature of the thermistor 8 increases, and at 25 degrees, the resistance of the thermistor 8 is R TH is 10 kΩ, and the resistance value R of the heater 7 h is 0.5kΩ, so it shows 0.48kΩ, and at 100 degrees the resistance value R of thermistor 8 TH is 0.7 kΩ, and the resistance value R of the heater 7 h Since is 0.5kΩ, it shows 0.29kΩ. In FIG. 8, the horizontal axis represents the temperature of the thermistor 8, that is, the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, and the vertical axis represents the resistance value R of the heater 7. h and the resistance value R of thermistor 8 TH Parallel resistance value R h / / R TH Shows.

[0084] Resistance value R of heater 7 h is constant regardless of temperature changes, and the resistance value R of the thermistor 8 TH changes significantly depending on the temperature, so as is clear from Figure 8, the parallel resistance R of the heater 7 and thermistor 8 h / / R TH and the temperature of the thermistor 8, that is, the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, are determined in a one-to-one relationship, and the parallel resistance value R h / / R TH changes, and the resistance value R of the thermistor 8 changes according to the change in the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6. TH can be read.

[0085] Resistance value R of thermistor 8 TH In this example, the resistance value R of the thermistor 8 is measured within the operating temperature range of the semiconductor laser 5 and the optical monitor 6. TH is the resistance value R of heater 7 h The parallel resistance R of the heater 7 and thermistor 8 is larger than h / / R TH is the parallel resistance value R in the operating temperature range h / / R TH It is set to change by 0.1% or more per degree change in temperature relative to the maximum value of .

[0086] That is, the parallel resistance R of the heater 7 and the thermistor 8 h / / R TH is the parallel resistance R within the operating temperature range h / / R TH The resistance value R of the thermistor 8 is set to satisfy the condition that the temperature changes by 0.1% or more per degree change of the maximum value of TH and the resistance value R of heater 7 h is designed to be close to the value. As a result, the resistance value R of thermistor 8 TH The measurement accuracy has improved.

[0087] Therefore, the parallel resistance R between the heater / thermistor common lead pin P6 and the ground lead pin P7 is h / / R TH of, Parallel resistance R within the operating temperature range h / / R TH The condition that the temperature changes by 0.1% or more per degree change of the maximum value of The control unit 9 passes a DC current between the heater / thermistor shared lead pin P6 and the ground lead pin P7, and measures the voltage between the heater / thermistor shared lead pin P6 and the ground lead pin P7 based on the DC current flowing between the heater / thermistor shared lead pin P6 and the ground lead pin P7, thereby obtaining the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6. The control unit 9 converts the analog voltage between the heater / thermistor common lead pin P6 and the ground lead pin P7 into a digital signal by an analog / digital converter (ADC) and uses it for control.

[0088] Furthermore, when the thermistor 8 detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, a direct current also flows through the heater 7. However, since the heater 7 is a low-power heater used to adjust the temperature of the ring resonator filter 64a in the optical filter 64, the heater 7 does not adversely affect the temperature of the semiconductor laser 5 or the temperature of the optical monitor 6.

[0089] In the preliminary preparation for operating the optical module, the thermistor 8 detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 without allowing a direct current to flow through the heater 7 for a long period of time, and from this point of view, the heater 7 does not have an adverse effect on the temperature of the semiconductor laser 5 or the temperature of the optical monitor 6. Furthermore, even when the optical module is in operation, the thermistor 8 detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6. However, this detection is performed periodically, periodically, or randomly, but for a short period of time, and therefore does not adversely affect the temperature of the semiconductor laser 5 or the temperature of the optical monitor 6 due to heating by the heater 7.

[0090] On the other hand, when the control unit 9 supplies a direct current between the heater / thermistor shared lead pin P6 and the ground lead pin P7 in adjusting the temperature of the ring resonator filter 64a during operation of the optical module, the resistance value R h is the resistance R of thermistor 8 TH Since the heater 7 is set to be small relative to thermistor 8, a larger current flows through the heater 7 than through the thermistor 8, making it easy to supply a current of the target value Ih_target to the heater 7 and facilitating temperature adjustment in the ring resonator filter 64a.

[0091] In short, in the optical module according to the first embodiment, the heater 7 and the thermistor 8 are electrically connected in parallel between the heater / thermistor common lead pin P6 and the ground lead pin P7. h and the resistance value R of thermistor 8 TH In this relationship, the resistance value R of thermistor 8 TH The resistance value R of the heater 7 is measured so that the change in h and the resistance value R of the heater 7 is set so that a larger current flows through the heater 7 than through the thermistor 8 when adjusting the temperature of the ring resonator filter 64a during operation of the optical module. h Since the lead pin P6 and the ground lead pin P7 are shared by the heater 7 and thermistor 8, the heater 7 and thermistor 8 have the same function as if they were connected to different lead pins at one end.

[0092] In this example, the heater 7 has a resistance value R h is the temperature-independent resistance R within the operating temperature range of the optical module. hThe heater 7 has a resistance value R h A heater having a characteristic that varies may also be used. The resistance value R h When a heater having a characteristic of changing resistance is used, the parallel resistance value R read by the control unit 9 is h / / R TH The control unit 9 calculates the resistance R of the heater 7 relative to the temperature. h The temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 can be obtained by correcting the change in the temperature. Alternatively, you can calculate the temperature and parallel resistance R h / / R TH The relationship between the temperature and the parallel resistance R h / / R TH The control unit 9 stores the relationship between the parallel resistance value R h / / R TH The temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 may be obtained by comparing the temperature with the relationship stored in the table.

[0093] As described above, the optical module according to the first embodiment comprises the temperature regulator 2 that performs the function of adjusting the temperature of the semiconductor laser 5, and the optical monitor 6 that performs the function of monitoring the optical output from the semiconductor laser 5 and the oscillation wavelength, and further comprises the heater 7 and thermistor 8, which are electrically connected in parallel and one end of the heater 7 and one end of the thermistor 8 are connected to the heater / thermistor shared lead pin P6. Therefore, the heater 7 and thermistor 8 are controlled substantially independently, and only one heater / thermistor shared lead pin P6 is required as the lead pin for the heater 7 and thermistor 8, except for the ground lead pin P7, and this allows for a compact optical module with advanced functions.

[0094] In short, the optical module according to embodiment 1 uses a single common lead pin P6 for both the heater 7 and thermistor 8, allowing heating by the heater 7 and temperature measurement and detection by the thermistor 8 to be performed independently, thereby enabling the optical module to be made smaller while improving its functionality as an optical module.

[0095] In the first embodiment, the heater 7 is used to adjust the temperature of the ring resonator filter 64a in the optical monitor 6, but it may also be used to adjust the temperature of other components or the temperature environment inside the package. Furthermore, in the first embodiment, the thermistor 8 is used to measure and detect the temperature of the semiconductor laser 5 and the optical monitor 6 in preparation for operating the optical module and during operation of the optical module, but it may also be used to measure and detect other components or the temperature environment within the package.

[0096] Embodiment 2 The optical module according to the second embodiment will be described with reference to FIG. The optical module of embodiment 2 differs from the optical module of embodiment 1 in that a capacitor 71 electrically connected in series with a heater 7 between the heater / thermistor shared lead pin P6 and the ground node, and an inductor 81 electrically connected in series with a thermistor 8 between the heater / thermistor shared lead pin P6 and the ground node are housed within package 1, but is otherwise the same or similar. In FIG. 12, the same reference numerals as those in FIG. 7 indicate the same or corresponding parts.

[0097] The following description will focus on the differences from the optical module according to the first embodiment. The capacitor 71 is electrically connected in series between the heater 7 and the lead pin P6 shared by the heater and thermistor. The inductor 81 is electrically connected in series between the thermistor 8 and the lead pin P6 shared by the heater and thermistor. The series combination of the heater 7 and capacitor 71 and the series combination of the thermistor 8 and inductor 81 are connected to a common lead pin P6 for both the heater and thermistor. and ground lead pin P7 and electrically connected in parallel between them.

[0098] When the optical module is in operation, the control unit 9 supplies an AC current between the heater / thermistor shared lead pin P6 and the ground lead pin P7 so that an AC current having a target value Ih_target flows through the heater 7, and the temperature of the ring resonator filter 64a is adjusted to a temperature at which the peak wavelength λfilt of the ring resonator filter 64a is obtained. Since an AC current is supplied between the heater / thermistor common lead pin P6 and the ground lead pin P7, no current flows through the series combination of the thermistor 8 and inductor 81. In short, AC power can be applied only to the series combination of the heater 7 and the capacitor 71 .

[0099] On the other hand, in preparation for operating the optical module in order to know with higher accuracy the relationship between the target value of the monitor value based on the laser light from the semiconductor laser 5 and the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6, when the control unit 9 supplies a DC current between the heater / thermistor shared lead pin P6 and the ground lead pin P7, the control unit 9 can obtain the resistance value between the heater / thermistor shared lead pin P6 and the ground lead pin P7 by measuring the DC voltage based on the DC current flowing between the heater / thermistor shared lead pin P6 and the ground lead pin P7, and can obtain the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 from the relationship in the characteristic diagram shown in Figure 11 which takes into account the resistance value of the inductor 81.

[0100] Since a direct current is supplied between the heater / thermistor common lead pin P6 and the ground lead pin P7, no current flows through the series combination of the heater 7 and capacitor 71. Since the resistance of the inductor 81 can be almost ignored, the resistance between the heater / thermistor common lead pin P6 and the ground lead pin P7 is the resistance R of the thermistor 8. TH is obtained as: In other words, DC power can be applied only to the series combination of the thermistor 8 and the inductor 81, and the resistance value R TH can be obtained.

[0101] When the optical module is in operation, the control unit 9 supplies a DC current between the heater / thermistor shared lead pin P6 and the ground lead pin P7, even when the thermistor 8 detects the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 periodically, periodically, or randomly. By supplying a direct current between the heater / thermistor common lead pin P6 and the ground lead pin P7, the resistance value R of the thermistor 8 is increased without flowing current into the series combination of the heater 7 and the capacitor 71. TH can be obtained.

[0102] As described above, the optical module according to the second embodiment, like the optical module according to the first embodiment, has the effect of being miniaturized as an optical module with advanced functions. Furthermore, in the optical module according to the second embodiment, when heating is performed by the heater 7, no current flows through the thermistor 8, and AC power can be applied only to the series combination of the heater 7 and the capacitor 71. When measuring and detecting the temperature by the thermistor 8, no current flows through the heater 7, and DC power can be applied only to the series combination of the thermistor 8 and the inductor 81. Furthermore, the resistance value R TH can be obtained.

[0103] As shown in FIG. 13, the optical module according to the first embodiment may be configured such that an inductor 72 electrically connected in series with the heater 7 is disposed between the heater / thermistor shared lead pin P6 and the ground node, and a capacitor 82 electrically connected in series with the thermistor 8 is disposed between the heater / thermistor shared lead pin P6 and the ground node.

[0104] In the optical module according to the second embodiment shown in FIG. 13 , when the optical module is in operation, the control unit 9 supplies a DC current between the heater / thermistor shared lead pin P6 and the ground lead pin P7 so that an AC current having a target value Ih_target flows through the heater 7. This allows DC power to be applied only to the series combination of the heater 7 and the inductor 72, and allows temperature adjustment of the ring resonator filter 64 a without flowing current through the series combination of the thermistor 8 and the capacitor 82.

[0105] On the other hand, when the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 are detected by the thermistor 8, if the control unit 9 supplies AC current between the heater / thermistor common lead pin P6 and the ground lead pin P7, AC power can be applied only to the series combination of the thermistor 8 and the capacitor 82, and the resistance value R of the thermistor 8 can be controlled without passing AC current through the series combination of the heater 7 and the inductor 72. TH can be obtained, and the temperature of the semiconductor laser 5 and the temperature of the optical monitor 6 can be detected and measured.

[0106] The modification of the optical module according to the second embodiment shown in FIG. 13 also has the same effects as the optical module according to the second embodiment.

[0107] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. [Industrial Applicability]

[0108] The optical module according to the present disclosure is suitable for use in a large-capacity optical communication system, and in particular, for use in a digital coherent communication system. Furthermore, the optical module according to the present disclosure is suitable for a TO-CAN type optical transmission module for optical communications that includes a single-wavelength semiconductor laser. [Explanation of symbols]

[0109] 1 package, 11 stem, 12 cap, 13 window, 2 temperature regulator, 3 base, 4 semiconductor laser submount, 5 semiconductor laser, 6 optical monitor, 61 optical coupler, 62 splitter, 63 first optical receiver, 64 optical filter, 65 second optical receiver, 7 heater, 71 capacitor, 72 inductor, 8 thermistor, 81 inductor, 82 capacitor, 9 control unit, P1 to P7 lead pins.

Claims

1. a package including a stem and a cylindrical cap with a window, the open end surface of the side wall of which is fixed in contact with the peripheral end of the inner flat surface of the stem; a semiconductor laser housed in the package and emitting laser light from the window of the windowed cap; an optical monitor housed in the package for receiving laser light from the semiconductor laser and monitoring the laser light from the semiconductor laser; a temperature regulator housed in the package for adjusting the temperature of the semiconductor laser and the temperature of the optical monitor, which controls the temperature applied to the semiconductor laser and the optical monitor when a monitor value from the optical monitor deviates from a set monitor value; a heater housed within the package; a thermistor housed in the package and electrically connected in parallel with the heater; a laser lead pin that penetrates the stem while being electrically insulated from the stem, and has an inner lead portion exposed from an inner flat surface of the stem to which an electrode of the semiconductor laser is connected; a monitor lead pin that penetrates the stem while being electrically insulated from the stem, and an output end of the optical monitor is connected to an inner lead portion exposed from an inner flat surface of the stem; a temperature controller lead pin that penetrates the stem while being electrically insulated from the stem, and an electrode of the temperature controller is connected to an inner lead portion exposed from an inner flat surface of the stem; a common lead pin for both the heater and thermistor, which penetrates the stem while being electrically insulated from the stem, and has an inner lead portion exposed from the inner plane of the stem, to which one end of the heater and one end of the thermistor are connected; a ground lead pin electrically connected to the stem; An optical module comprising:

2. the temperature regulator is mounted on the stem; a base having a vertical surface portion that is mounted and fixed on a mounting surface of the temperature controller and on which the semiconductor laser is mounted and fixed, a flat surface portion that is formed integrally with the vertical surface portion and on which the optical monitor is mounted and fixed at a position where the optical monitor receives rear laser light from the semiconductor laser, and a stepped portion that is formed on the opposite side of the vertical surface of the vertical surface portion and has a mounting surface that is a horizontal surface on which the thermistor is mounted and fixed, 2. The optical module according to claim 1.

3. the optical monitor has a first optical receiver that receives laser light from the semiconductor laser, an optical filter that receives the laser light from the semiconductor laser, and a second optical receiver that receives the laser light via the optical filter; the monitor lead pins are configured by a lead pin to which an output terminal of the first optical receiver is connected and a lead pin to which an output terminal of the second optical receiver is connected; 2. The optical module according to claim 1.

4. the temperature controller is a thermoelectric cooler configured by a Peltier element having a positive electrode and a negative electrode, the temperature regulator lead pins are composed of a lead pin to which a positive electrode of the temperature regulator is connected and a lead pin to which a negative electrode of the temperature regulator is connected; 2. The optical module according to claim 1.

5. The thermistor has a characteristic of a resistor whose resistance value changes depending on temperature, 5. An optical module according to claim 1, wherein the resistance value of the thermistor is greater than the resistance value of the heater within the operating temperature range of the semiconductor laser and the optical monitor, and is not more than 70 times the resistance value of the heater.

6. The thermistor has a characteristic of a resistor whose resistance value changes depending on temperature, the heater has a constant resistance value within the operating temperature range of the semiconductor laser and the optical monitor; In the operating temperature range, the resistance value of the thermistor is greater than the resistance value of the heater, and the parallel resistance value of the thermistor and the heater changes by 0.1% or more per degree change in temperature from the maximum value of the parallel resistance value of the thermistor and the heater in the operating temperature range. The optical module according to any one of claims 1 to 4.

7. the optical monitor is a planar waveguide type optical monitor having an optical coupler, a demultiplexer, a first optical receiver, an optical filter, and a second optical receiver, and the monitored value from the optical monitor has a first monitored value and a second monitored value; the first optical receiver receives the laser light from the semiconductor laser via the optical coupler, receives one of the laser lights branched from the branching filter via an optical waveguide, performs photoelectric conversion on the received light, and outputs the first monitor value to an output terminal; the second optical receiver receives the laser light from the semiconductor laser received by the optical coupler, receives the laser light obtained by filtering the other laser light separated by the demultiplexer by the optical filter, performs photoelectric conversion on the received light, and outputs the second monitor value to an output terminal; the monitor lead pin is composed of a lead pin to which an output terminal of the first optical receiver is connected and a lead pin to which an output terminal of the second optical receiver is connected; the heater heats the optical monitor to adjust the temperature of the optical monitor; 2. The optical module according to claim 1.

8. The thermistor has a characteristic of a resistor whose resistance value changes depending on temperature, 8. The optical module according to claim 7, wherein the resistance value of the thermistor is greater than the resistance value of the heater within the operating temperature ranges of the semiconductor laser and the optical monitor, and is not more than 70 times the resistance value of the heater.

9. The thermistor has a characteristic of a resistor whose resistance value changes depending on temperature, the heater has a constant resistance value within the operating temperature range of the semiconductor laser and the optical monitor; In the operating temperature range, the resistance value of the thermistor is greater than the resistance value of the heater, and the parallel resistance value of the thermistor and the heater changes by 0.1% or more per degree change in temperature from the maximum value of the parallel resistance value of the thermistor and the heater in the operating temperature range.

8. The optical module according to claim 7.

10. a capacitor electrically connected in series with the heater between the heater / thermistor common lead pin and a ground node; an inductor electrically connected in series with the thermistor between the heater / thermistor common lead pin and the ground node; 10. The optical module according to claim 1, further comprising:

11. an inductor electrically connected in series with the heater between the heater / thermistor common lead pin and a ground node; a capacitor electrically connected in series with the thermistor between the heater / thermistor common lead pin and the ground node; 10. The optical module according to claim 1, further comprising:

12. 10. The optical module according to claim 1, wherein the stem is a metal disk having a diameter of 5.6 mm, and the windowed cap is cylindrical.

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