JP6173206B2 - Optical integrated device - Google Patents

Description

The present invention relates to an optical integrated device Ru comprising a tunable optical source by integrating a plurality of semiconductor lasers.

  In recent years, with a dramatic increase in communication demand, a large-capacity optical fiber communication system is demanded, and a single mode capable of obtaining a high side mode suppression ratio (SMSR) of at least 30 to 40 dB or more. Wavelength division multiplexing communication system that enables large-capacity transmission over a single optical fiber by multiplexing a plurality of signal lights having different wavelengths using an LD (Laser Diode) (hereinafter referred to as a single mode LD) Is realized.

  Examples of the single mode LD include a distributed feedback laser diode (hereinafter referred to as DFB-LD) and a distributed Bragg reflector laser diode (hereinafter referred to as DBR-LD). .

  In order to reduce the cost of the wavelength division multiplexing communication system, a low-cost tunable light source that covers the entire wavelength band is required, and a tunable light source in which a single mode LD is monolithically integrated on the same substrate. It is attracting attention as a candidate.

  Normally, the above-mentioned wavelength tunable light source is used in combination with an external modulator module that generates a data signal, but other than that, an electro absorption (EA) type optical modulator or a Mach Zehnder (MZ) type optical modulation. Research has also been conducted on monolithic integration of vessels on the same substrate.

  Conventionally, the output side of a plurality of DFB-LDs is connected to an input waveguide of a multimode interference (Multi Mode Interference) type optical multiplexing circuit (hereinafter referred to as MMI), and the light multiplexed by the MMI is output from the output waveguide. A variable wavelength light source configured to output is disclosed (for example, see Patent Document 1). In the following, the MMI of K input (K is a natural number) and L output (L is a natural number) will be referred to as K × L-MMI. That is, the K input refers to K input waveguides connected to the MMI, and the L output refers to L output waveguides connected to the MMI.

  Also disclosed is a wavelength tunable light source in which the output sides of a plurality of LDs are connected to N × 2-MMI (N is a natural number of 3 or more), and two output waveguides of MMI are connected to two arms of a Mach-Zehnder modulator. (For example, refer to Patent Document 2). According to Patent Document 2, it is possible to improve the optical loss as compared with the case of using N × 1-MMI.

  Further, there is disclosed a wavelength tunable light source in which a wavelength tunable laser diode and a wavelength monitor are integrally integrated, and light output from behind the wavelength tunable laser diode is input to the wavelength monitor via a waveguide (for example, a patent) Reference 3). According to Patent Document 3, it is possible to configure a small wavelength variable light source module.

Japanese Patent No. 3888744 Japanese Patent No. 4728746 JP 2013-89961 A

  In recent years, digital coherent communication using optical phase modulation is being put into practical use in a wavelength division multiplexing communication system having a transmission rate of 40 Gbps or more in a trunk line system. In a wavelength division multiplex communication system employing digital coherent communication, a narrow linewidth variable wavelength light source having a laser oscillation line width of 1 MHz or less, more preferably 500 kHz or less is used as a light source for transmission and reception.

  In wavelength division multiplex communication employing the above digital coherent communication, if the wavelengths of optical signals used for transmission and reception are different, separate wavelength variable light sources are required for transmission and reception. The power consumption of the entire transmission / reception device including the light source increases.

  On the other hand, in the wavelength division multiplex communication employing the above-mentioned digital coherent communication, there are many cases where the wavelengths of optical signals used for transmission and reception are the same, which is generally required for transmission and reception. The light output of the line width variable wavelength light source is different. In such a case, it is desirable to use one tunable light source as a light source for transmission and reception from the viewpoint of reducing power consumption of the entire transmission and reception device and reducing the mounting area.

  For example, in the case where the wavelength tunable light source disclosed in Patent Documents 1 to 3 is also used as a light source for transmission and reception, the wavelength tunable light source disclosed in Patent Documents 1 to 3 needs to have two outputs by a polarization maintaining coupler. However, in such a configuration, a branching loss occurs in the polarization maintaining coupler. Therefore, in order to compensate for the branching loss, a semiconductor optical amplifier (hereinafter referred to as SOA) provided on the output side of the wavelength tunable light source is used. ) To increase the light output from the wavelength tunable light source, but this causes a problem of increasing power consumption and laser oscillation line width.

The present invention has been made in order to solve these problems, and is an optical integrated circuit provided with a wavelength tunable light source that can also be used as a light source for transmission and reception and can suppress an increase in laser oscillation line width and power consumption. An object is to provide an element.

In order to solve the above problems, an optical integrated device according to the present invention has a first input side and a first output side, and one ends of a plurality of first input waveguides are connected to the first input side. The first output waveguide is connected to the first output end, and the first light input from each first input waveguide is multiplexed, and the combined first light is the first A first optical multiplexing circuit that outputs to the output waveguide, a second input side and a second output side, and one end of a plurality of second input waveguides is connected to the second input side, A second output waveguide is connected to the second output side, and the second light input from each second input waveguide is multiplexed, and the combined second light is output to the second output. The second optical multiplexing circuit that outputs to the waveguide, one end is connected to the other end of each first input waveguide, the other end is connected to the other end of each second input waveguide, and each has a different wavelength A plurality of semiconductor lasers capable of single mode oscillation; a first optical amplifier connected to the first output waveguide; and a second optical amplifier connected to the second output waveguide. There are a plurality of output waveguides or second output waveguides including a monitoring output waveguide for monitoring the oscillation wavelength of the output light of the semiconductor laser, a tunable light source, a modulator, and a receiver An amplification factor of the first optical amplifier is larger than an amplification factor of the second optical amplifier, and the modulator is connected to the first optical amplifier of the wavelength tunable light source and receives The instrument is connected to a second optical amplifier of the wavelength tunable light source .

According to the present invention, the wavelength tunable light source has a first input side and a first output side, one end of a plurality of first input waveguides is connected to the first input side, and the first output end Are coupled to the first output waveguide and combine the first light input from the first input waveguides, and output the combined first light to the first output waveguide. A first optical multiplexing circuit; a second input side; and a second output side; one end of a plurality of second input waveguides connected to the second input side; Second output waveguides are connected to each other, combine the second light input from each second input waveguide, and output the combined second light to the second output waveguide. And one end connected to the other end of each first input waveguide and the other end connected to the other end of each second input waveguide, each capable of single mode oscillation at a different wavelength. A plurality of semiconductor lasers, a first optical amplifier connected to the first output waveguide, and a second optical amplifier connected to the second output waveguide. The output waveguide 2 includes a plurality of variable wavelength light sources including a monitoring output waveguide for monitoring the oscillation wavelength of the output light of the semiconductor laser, an optical integrated device including a modulator and a receiver The amplification factor of the first optical amplifier is larger than the amplification factor of the second optical amplifier, the modulator is connected to the first optical amplifier of the wavelength variable light source, and the receiver is the wavelength variable light source. second to be connected to the optical amplifier, it is possible to also serves as a wavelength-variable light source as the light source for receiving and suppress an increase in the laser oscillation linewidth and power consumption.

It is a figure which shows an example of a structure of the wavelength variable light source by Embodiment 1 of this invention. It is a figure which shows an example of a structure of the wavelength variable light source by Embodiment 2 of this invention. It is a figure which shows an example of a structure of the wavelength variable light source by Embodiment 3 of this invention. It is a figure which shows an example of a structure of the wavelength variable light source by Embodiment 4 of this invention. It is a figure which shows an example of a structure of the optical integrated element by Embodiment 5 of this invention. It is a figure which shows an example of a structure of the wavelength variable light source module by Embodiment 6 of this invention. It is a figure which shows an example of a structure of the transmission / reception apparatus by Embodiment 7 of this invention. It is a figure which shows an example of a structure of the wavelength variable light source by a prerequisite technique. It is sectional drawing which shows an example of a structure of the MMI input waveguide in the wavelength variable light source by a premise technique. It is sectional drawing which shows an example of a structure of SOA in the wavelength tunable light source by a base technology. It is a figure which shows an example of a structure of the transmitter / receiver by a premise technique. It is a figure which shows an example of a structure of the wavelength variable light source module by a prerequisite technique.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following, the same or similar components in each drawing are given the same reference numerals or the same names, and their functions are also the same.

  In addition, the dimensions, materials, shapes, and relative arrangements of the components exemplified in the embodiments are appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. However, the present invention is not limited to these examples.

<Prerequisite technology>
First, a technique (a prerequisite technique) which is a premise of the present invention will be described.

  FIG. 8 is a diagram showing an example of the configuration of a wavelength tunable light source according to the base technology, and shows an example of the configuration of a wavelength tunable light source using a plurality of single mode LDs having different oscillation wavelengths.

  The DFB-LD array 11 includes N DFB-LDs 10 and is connected to N × 1-MMI 30 (N is a natural number of 3 or more) MMI input waveguides 31.

  The SOA 60 is connected to the MMI output waveguide 32 of N × 1-MMI30.

  In the above configuration, when any DFB-LD 10 in the DFB-LD array 11 is laser-oscillated, 1 / N of light output from the DFB-LD 10 (hereinafter referred to as LD output light) is MMI output waveguide 32. And the remaining (N−1) / N is radiated out of the MMI output waveguide 32. Compensation for branch loss, coupling loss, and the like is performed by injecting current into the SOA 60, and a high transmission optical output 70 is output from the SOA 60 to the outside.

  FIG. 9 is a cross-sectional view showing an example of the AA cross section of FIG. 8, and shows an example of the configuration of the MMI input waveguide 31.

  The MMI input waveguide 31 is formed by sequentially laminating an InP lower cladding layer 41, an InP current blocking layer 44, an InGaAsP waveguide layer 42, and an InP upper cladding layer 43 on an InP substrate 40.

  The InGaAsP waveguide layer 42 is made of an InGaAsP-based material that does not absorb LD output light. The InGaAsP waveguide layer 42 may be a bulk epitaxial layer or a multiple quantum well (MQW) layer.

  Although FIG. 9 shows the configuration of the MMI input waveguide 31, the configuration of the MMI output waveguide 32 is the same.

  Further, in the configuration of the N × 1-MMI 30 in the wide multimode region, the width of the InGaAsP waveguide layer 42 (width in the horizontal direction in FIG. 9) is wider than that of the MMI input waveguide 31 and the MMI output waveguide 32. The configuration is the same as that of the MMI input waveguide 31 and the MMI output waveguide 32.

  FIG. 10 is a cross-sectional view showing an example of the BB cross section of FIG. 8, and shows an example of the configuration of the SOA 60.

  The SOA 60 is formed by sequentially laminating a lower cladding layer 41, an InP current blocking layer 44, an InGaAsP active layer 45, an InP upper cladding layer 43, and an InGaAsP contact layer 46 on an InP substrate 40.

  For the InGaAsP active layer 45, an InGaAsP material having a gain with respect to light passing through the MMI output waveguide 32 (hereinafter referred to as guided light) is used. The InGaAsP active layer 45 may be a bulk epitaxial layer or a multiple quantum well (MQW) layer.

  In addition, although FIG. 10 shows the configuration of the SOA 60, the configuration of the DFB-LD 10 is the same. In the DFB-LD 10 and the SOA 60, when current injection is performed through electrodes (not shown) provided on the InP substrate 40 and the InGaAsP contact layer 46, a gain is generated in the InGaAsP active layer 45 and spontaneous emission light is generated. In the DFB-LD 10, spontaneous emission light of a specific wavelength reflected by the diffraction grating becomes stimulated emission seed light, and laser oscillation occurs when a predetermined threshold current is exceeded. On the other hand, the SOA 60 functions as an amplifier for the LD output light, but is designed not to oscillate alone.

  The oscillation wavelength of the DFB-LD 10 changes at a rate of about 0.1 nm / ° C. according to the temperature of the DFB-LD 10 (hereinafter referred to as element temperature). Therefore, when the element temperature is changed within a predetermined range (for example, 10 ° C. to 50 ° C.), any of the DFB-LD arrays 11 among the N (for example, N = 10 to 16) DFB-LD arrays 11 The interval between the oscillation wavelengths of each DFB-LD 10 is designed so that the oscillation wavelength matches the oscillation wavelength of another adjacent DFB-LD 10. At this time, the combination of the selection of the DFB-LD 10 and the adjustment of the element temperature allows the DFB-LD array 11 formed in one chip to use the entire wavelength band (about 30 nm to about C band (Conventional band) or L band (Long band)). 40 nm).

  In FIGS. 9 and 10, an InGaAsP material on an InP substrate used in a long wavelength optical communication element is shown as an example, but an InAlGaAs material may be used.

  FIG. 11 is a diagram illustrating an example of the configuration of the transmission / reception device 80 according to the base technology, and illustrates the configuration of the transmission / reception device 80 for a digital coherent communication system.

  The transmission optical output 71 output from the wavelength variable light source module 91 is modulated by the modulator module 81 and then output to the outside as a transmission signal 73.

  Further, the received signal 74 received from the outside is input to the receiver module 82 together with the receiving light output 72 output from the wavelength variable light source module 91, and is restored after the signal processing.

  In the transmission / reception apparatus 80 shown in FIG. 11, insertion loss occurs in the modulator module 81. Therefore, the transmission optical output 71 generally requires a high output, but the reception optical output 72 has a relatively low output. There may be.

  However, as described above, when the wavelengths of optical signals used for transmission and reception are the same, one wavelength variable light source module is used for transmission / reception from the viewpoint of reducing the power consumption of the entire transmission / reception device 80 and reducing the mounting area. It is desirable to also use as a light source.

  FIG. 12 is a diagram showing an example of the configuration of the wavelength tunable light source module 91 according to the base technology. The wavelengths of optical signals used for transmission and reception are the same, and one wavelength tunable light source module 91 is used for transmission and reception. The structure in the case of being used also as a light source is shown.

  The wavelength tunable light source module 91 includes a wavelength tunable light source 90, a coupling optical system 92, a beam splitter 95, and a monitor 96. Further, an optical fiber 93 and a polarization maintaining coupler 94 are connected to the LD output side of the wavelength tunable light source module 91.

  The wavelength variable light source 90 emits single mode LD output light, and the emitted LD output light is coupled to an optical fiber 93 via a coupling optical system 92 including a lens, an optical isolator (not shown), and the like. The LD output light coupled to the optical fiber 93 is branched at a predetermined ratio by the polarization maintaining coupler 94, and each of the branched LD output lights is output as a transmission light output 71 and a reception light output 72.

  Further, part of the LD output light that passes through the coupling optical system 92 is extracted by the beam splitter 95, and the wavelength and output level of the LD output light by the monitor 96 including a wavelength filter, a photodiode, and the like (not shown). Is detected.

  In the above configuration, since the wavelength variable light source 90 has one output, the polarization maintaining coupler 94 makes two outputs. However, in such a configuration, a branching loss occurs in the polarization maintaining coupler 94. Therefore, an injection current for an SOA (not shown) provided on the output side of the wavelength tunable light source 90 is increased to compensate for the branching loss. Therefore, it is necessary to increase the output of the LD output light from the wavelength tunable light source 90. However, there is a problem that the power consumption and the laser oscillation line width are increased.

  The present invention has been made to solve such problems, and will be described in detail below.

<Embodiment 1>
FIG. 1 is a diagram showing an example of the configuration of a wavelength tunable light source 98 according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the wavelength tunable light source 98 according to the first embodiment includes a DFB-LD array composed of 12 DFB-LDs 10 (semiconductor lasers), a first input waveguide 33 and a second input waveguide 33. An input waveguide 34, a first optical multiplexing circuit 35 and a second optical multiplexing circuit 36 that are 12 × 1-MMI, a first output waveguide 37 and a second output waveguide 38, An SOA 61 (first optical amplifier) and a second SOA 62 (second optical amplifier) are provided.

  In FIG. 1, eight DFB-LDs 10 are shown for simplicity of illustration, but it is assumed that there are actually twelve as described above. The same applies to the first input waveguide 33, the second input waveguide 34, the first optical multiplexing circuit 35, and the second optical multiplexing waveguide 36. The same applies to other embodiments unless otherwise specified.

  The difference from the wavelength tunable light source according to the base technology shown in FIG. 8 is that the first input waveguide 33 and the first optical multiplexing circuit 35, the second input waveguide 34 and the second optical waveguide are located at both ends of each DFB-LD 10. The optical multiplexing circuit 36 is connected to each other.

  The first optical multiplexing circuit 35 has an input side (first input side) and an output side (first output side), and one end of twelve first input waveguides 33 is connected to the input side. The first output waveguide 37 is connected to the output side, and LD output light (first light) input from each first input waveguide 33 is multiplexed, and the combined LD The output light is output to the first output waveguide 37.

  The second optical multiplexing circuit 36 has an input side (second input side) and an output side (second output side), and one end of twelve second input waveguides 34 is connected to the input side. , One second output waveguide 38 is connected to the output side, and LD output light (second light) input from each second input waveguide 34 is multiplexed, and the combined LD The output light is output to the second output waveguide 38.

  The twelve DFB-LDs 10 have one end connected to the other end of each first input waveguide 33 and the other end connected to the other end of each second input waveguide 34. Mode oscillation is possible.

  The first SOA 61 is connected to the first output waveguide 37.

  The second SOA 62 is connected to the second output waveguide 38.

  The first SOA 61 and the second SOA 62 are the same waveguide type except for the length (the length in the LD output light passage direction), and the first SOA 61 is longer than the second SOA 62. Further, a current injection mechanism (not shown) is independently connected to each of the first SOA 61 and the second SOA 62.

  The first SOA 61 and the second SOA 62 are formed by removing a predetermined portion of the first output waveguide 37 and the second output waveguide 38 by etching, and then performing the first growth by a regrowth technique called butt joint growth. The cross section of the output waveguide 37 and the cross section of the first SOA 61, and the cross section of the second output waveguide 38 and the cross section of the second SOA 62 are formed so as to be directly joined.

  In order to suppress the generation of reflected return light at the output ends of the first output waveguide 37 and the second output waveguide 38, a non-reflective coating (not shown) is applied to the output end face. By suppressing the generation of reflected return light, an increase in the laser oscillation line width can be suppressed. At this time, at least one of the first output waveguide 37 and the second output waveguide 38 may be formed as a curved waveguide on the output end side. With such a configuration, the generation of reflected return light can be further suppressed.

  The configurations of the first input waveguide 33 and the second input waveguide 34 are the same as those shown in FIG. 9, and the configurations of the first SOA 61, the second SOA 62, and the DFB-LD 10 are shown in FIG. Since it is the same as the structure shown, description is abbreviate | omitted here.

  Next, the operation of the wavelength tunable light source will be described.

  When an arbitrary DFB-LD 10 is selected and current injection exceeding the threshold current is performed, laser oscillation occurs in the selected DFB-LD 10. The LD output light output from the DFB-LD 10 passes through the first input waveguide 33 and the second input waveguide 34, and the multimode region of the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36. Is input. As will be described later (see Embodiment 3), if the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36 are appropriately designed, the first optical multiplexing circuit 35 and the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36 are designed over the entire wavelength band. Each of the two optical multiplexing circuits 36 can couple the LD output light at a ratio of about 1/12, which is substantially the same as that of the DFB-LD 10 (see FIG. 8) according to the base technology. Therefore, it is not necessary to increase the drive current as compared with the DFB-LD 10 according to the base technology (that is, the drive current of the DFB-LD 10 may be the same as that of the base technology).

  When current is injected into the first SOA 61 and the second SOA 62, each LD output light traveling through the first output waveguide 37 and the second output waveguide 38 is amplified, and the current value is increased when the current value is increased. The amplification factors in the first SOA 61 and the second SOA 62 also increase. The amplification factor is expressed by logarithmically expressing the output light intensity based on the input light, but generally exhibits a non-linear behavior. That is, when the input light is weak (low output), the amplification factor is substantially constant. However, when the input light is strong (high output), the amplification factor decreases, so that the maximum output tends to be saturated with the input light intensity. The saturation outputs per unit length of the first SOA 61 and the second SOA 62 are the optical confinement coefficients and currents of the active layers of the first SOA 61 and the second SOA 62 (corresponding to the InGaAsP active layer 45 in FIG. 10). It depends on the density. Therefore, if the optical confinement coefficients and current densities of the active layers of the first SOA 61 and the second SOA 62 are the same, the maximum outputs of the first SOA 61 and the second SOA 62 are the first SOA 61 and the second SOA 62, respectively. Is determined by the length of

  As shown in FIG. 1, the length of the first SOA 61 is longer than the length of the second SOA 62, and the width of the active layer and the optical confinement factor are the same. Therefore, the maximum output at the same current density is higher in the first SOA 61 than in the second SOA 62. That is, the first SOA 61 has a higher amplification factor than the second SOA 62.

  As described above, in the transmission / reception apparatus for the digital coherent communication system, the reception optical output 72 may be lower than the transmission optical output 71. Therefore, the light amplified by the first SOA 61 is used as the transmission optical output 71. The light amplified by the second SOA 62 can be used as the reception light output 72.

  In other words, if the length of the first SOA 61 is the same as that of the SOA 60 (see FIG. 8) according to the premise technology, the drive current of the DFB-LD 10 and the first current are required to obtain the equivalent transmission optical output 71. The injection current for the SOA 61 is the same, and the injection current for the second SOA 62 required to obtain the reception optical output 72 is smaller than the base technology. Therefore, when one wavelength tunable light source 98 according to the first embodiment shown in FIG. 1 is used for a transmission / reception device, power consumption is higher than that of the transmission / reception device 80 (FIG. 11) based on the premise technique using a separate wavelength tunable light source. Can be reduced to 1/2 or less.

  Further, in the wavelength tunable light source 98 shown in FIG. 1, a non-reflective coating is applied to the output end face in order to suppress the generation of reflected return light at the output ends of the first output waveguide 37 and the second output waveguide 38. Has been. However, when the amplification factors of the first SOA 61 and the second SOA 62 are increased in order to obtain a high output, the slight reflected return light reflected from the output end face is amplified by the first SOA 61 and the second SOA 62. There is a possibility of returning to the DFB-LD 10 side and destabilizing the oscillation state of each DFB-LD 10 to increase the laser oscillation line width. As a countermeasure against such a problem, in the first embodiment, the gain (amplification factor) of the second SOA 62 is set low to suppress the amplification of the reflected return light from the output end face, and the laser oscillation line width is reduced. It is possible to suppress the increase.

  From the above, according to the first embodiment, it is possible to use the variable wavelength light source as a light source for transmission and reception, and to suppress an increase in laser oscillation line width and power consumption.

<Embodiment 2>
FIG. 2 is a diagram showing an example of the configuration of the wavelength tunable light source 98 according to Embodiment 2 of the present invention.

  As shown in FIG. 2, the wavelength tunable light source 98 according to the second embodiment has a first output waveguide 37 and a second output waveguide 38 that have an arc shape and the same output end as the wavelength tunable light source 98. It is characterized by being formed to exist on the end face side. Other configurations and operations are the same as those in the first embodiment (see FIG. 1), and thus description thereof is omitted here.

  The first output waveguide 37 and the second output waveguide 38 are formed in an arc shape set to a radius capable of suppressing transmission loss of LD output light.

  Each of the transmission light output 71 and the reception light output 72 is output with an interval of several millimeters from the end face of the wavelength variable light source 98 in the same direction, and is coupled to an optical fiber via a separate coupling optical system. Can do.

  From the above, according to the second embodiment, in addition to the effects of the first embodiment, transmission loss of LD output light can be suppressed. Further, since the transmission light output 71 and the reception light output 72 are output from the same end face side of the wavelength variable light source 98, an array type optical component such as a lens array can be used, and the optical system is reduced in size and cost. can do.

<Embodiment 3>
FIG. 3 is a diagram showing an example of the configuration of the wavelength tunable light source 98 according to Embodiment 3 of the present invention.

  As shown in FIG. 3, the wavelength tunable light source 98 according to the third embodiment is characterized in that the second optical multiplexing circuit 36 is 12 × 2-MMI. Other configurations and operations are the same as those in the first embodiment (see FIG. 1), and thus description thereof is omitted here.

  A second output waveguide 38 in which a second SOA 62 is formed and a monitor output waveguide 39 are connected to the output side of the second optical multiplexing circuit 36.

  An SOA is not formed in the monitor output waveguide 39 and is used to output the monitor optical output 75.

  Here, the width of the multimode region of the second optical multiplexing circuit 36 of N × 2-MMI (N = 12) (the width of the input end face on the input side and the output end face on the output side of the second optical multiplexing circuit 36). The width in the vertical direction of the paper surface in FIG. 3 is W, and the length (the length of the surface orthogonal to the input end surface and the output end surface, the length in the horizontal direction of the paper surface in FIG. 3) is L.

  The arrangement positions of the twelve second input waveguides 34 are symmetrical with the center of the width of the multimode region of the second optical multiplexing circuit 36 as the origin (coordinate 0) (centered around the input end face W / 2), and They are arranged at intervals of W / N. In addition, the two second input waveguides 34 on the outer sides are located at a position W / (2N) from the end of the multimode region of the second optical multiplexing circuit 36, that is, coordinates (W / 2−W / 24, -W / 2 + W / 24). The first input waveguide 33 is also arranged in the same manner.

  On the other hand, the second output waveguide 38 and the monitor output waveguide 39 are also arranged symmetrically and at intervals of W / N around the output end face W / 2, and in the example of FIG. The input waveguides 34 are arranged at the same central symmetry position as the two second input waveguides 34 arranged in the center, that is, at coordinates (± W / 24).

  Note that the length L of the multimode region of the second optical multiplexing circuit 36 (12 × 2-MMI) shown in FIG. 3 is the same as that in FIG. 1 when the second input waveguide 34 is arranged in the same manner as described above. It may be substantially the same as the optimum value of the length L of the second optical multiplexing circuit 36 (12 × 1-MMI) shown.

  Next, the operation of the wavelength tunable light source will be described.

  When an arbitrary DFB-LD 10 is selected and current injection exceeding the threshold current is performed, laser oscillation occurs in the selected DFB-LD 10. The LD output light output from the DFB-LD 10 passes through the first input waveguide 33 and the second input waveguide 34, and the multimode region of the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36. Is input. As described above, if the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36 are appropriately designed, the first output waveguide 37 and the second output waveguide 38 over the entire wavelength band. LD output light can be coupled to the monitor output waveguide 39 at a ratio of about 1/12, which is approximately the same level as the DFB-LD10 (see FIG. 8) according to the base technology. It is not necessary to increase the drive current as compared with the LD 10 (that is, the drive current of the DFB-LD 10 may be the same as that of the base technology).

  When current is injected into the first optical multiplexing circuit 35 and the second optical multiplexing circuit 36, the LD output light traveling through the first output waveguide 37 and the second output waveguide 38 is amplified, and the first The light amplified by the first SOA 61 is used as the transmission optical output 71, and the light amplified by the second SOA 62 is used as the reception optical output 72.

  Further, the monitoring optical output 75 can be used for monitoring the optical output of the LD output light or the oscillation wavelength by receiving light with an appropriate combination of a photodiode and an etalon.

  From the above, according to the third embodiment, in addition to the effects of the first embodiment, it is possible to monitor the oscillation wavelength and light output of the LD output light. Further, since it is not necessary to branch the LD output light for monitoring, insertion loss can be reduced.

<Embodiment 4>
FIG. 4 is a diagram showing an example of the configuration of the wavelength tunable light source 98 according to Embodiment 4 of the present invention.

  As shown in FIG. 4, the wavelength tunable light source 98 according to the fourth embodiment is characterized in that the second optical multiplexing circuit 36 is 12 × 2-MMI. Other configurations and operations are the same as those of the second embodiment (see FIG. 2), and thus description thereof is omitted here.

  A second output waveguide 38 in which a second SOA 62 is formed and a monitor output waveguide 39 are connected to the output side of the second optical multiplexing circuit 36.

  An SOA is not formed in the monitor output waveguide 39 and is used to output the monitor optical output 75.

  The monitor output waveguide 39 has an arc shape set to a radius capable of suppressing transmission loss of LD output light, and the output ends thereof are the first output waveguide 37 and the second output waveguide 38. It is formed so as to exist on the end face side of the wavelength tunable light source 98 different from the output end side. That is, the monitoring light output 75 is output in a direction different from the transmission light output 71 and the reception light output 72, and then input to the photodiode or etalon.

  From the above, according to the fourth embodiment, in addition to the effects of the second embodiment, it is possible to monitor the oscillation wavelength and the optical output of the LD output light. Further, since it is not necessary to branch the LD output light for monitoring, insertion loss can be reduced.

<Embodiment 5>
FIG. 5 is a diagram showing an example of the configuration of the optical integrated device 99 according to the fifth embodiment of the present invention.

  As shown in FIG. 5, the optical integrated device 99 according to the fifth embodiment includes a wavelength variable light source 98, an optical phase modulator 50 (modulator), an optical 90-degree hybrid circuit 51 (receiver), and a photodiode. 52. Note that the wavelength variable light source 98 is the same as that of the third embodiment (FIG. 3), and thus the description thereof is omitted here. In addition, each component is assumed to be integrated on one chip.

  The optical phase modulator 50 is connected to the first output waveguide 37, modulates the transmission optical output 71 output from the first SOA 61, and outputs the modulated signal as a transmission signal 73.

  The optical 90-degree hybrid circuit 51 is connected to the second output waveguide 38, and includes a reception optical output 72 output from the second SOA 62, and a reception signal 74 input from the outside of the optical integrated device 99. Interference light having a light intensity signal is generated.

  The photodiode 52 converts the interference light output from the optical 90-degree hybrid circuit 51 into an electrical signal and outputs the electrical signal.

  From the above, according to the fifth embodiment, an optical integrated device capable of transmitting and receiving can be realized.

  In the fifth embodiment, the wavelength variable light source 98 according to the third embodiment is described as an example of the wavelength variable light source 98. However, the present invention is not limited to this. For example, the same effect as described above can be obtained even if the wavelength tunable light source 98 according to the first, second, and fourth embodiments is used as the wavelength tunable light source 98 according to the fifth embodiment.

<Embodiment 6>
FIG. 6 is a diagram showing an example of the configuration of the wavelength light source module 97 according to Embodiment 6 of the present invention.

  The sixth embodiment is characterized in that any one of the variable wavelength light sources 98 according to the first to fourth embodiments is used as the variable wavelength light source 98 of the variable wavelength light source module 97. Other configurations and operations of the wavelength tunable light source module 97 are the same as those of the wavelength tunable light source module 91 (see FIG. 12) according to the base technology, and thus the description thereof is omitted here.

  FIG. 6 shows an example in which the variable wavelength light source 98 according to Embodiment 1 is used.

  As shown in FIG. 6, the wavelength tunable light source 98 outputs a transmission light output 71 and a reception light output 72 from separate output ports. The transmission light output 71 and the reception light output 72 output from the wavelength variable light source 98 are respectively coupled to the optical fiber 93 by a coupling optical system 92 including a lens, an optical isolator (not shown), and the like. That is, the wavelength tunable light source module 97 separately takes out each of the transmission light output 71 and the reception light output 72 (a plurality of output lights) output from the wavelength tunable light source 98.

  Further, a part of the light (output light) of the transmission light output 71 output from the wavelength variable light source 98 is extracted by the beam splitter 95 and includes a wavelength filter, a photodiode, and the like (not shown). 96 is used to detect the wavelength and output level.

  From the above, according to the sixth embodiment, the polarization maintaining coupler 94 provided on the output side of the wavelength tunable light source module 91 according to the base technology is unnecessary and insertion loss is reduced (that is, the transmission optical output 71). And the receiving optical output 72 are coupled to the separate optical fiber 93 by the separate coupling optical system 92), the gain (amplification factor) of the second SOA 62 is set to be low in the wavelength variable light source 98. Light intensity can be obtained. Therefore, it is possible to suppress amplification of reflected return light from the second SOA 62 to each DFB-LD 10 in the wavelength tunable light source 98 and suppress an increase in the laser oscillation line width.

  In the above description, the case where the wavelength tunable light source 98 according to Embodiment 1 is used has been described as an example. However, the wavelength tunable light source 98 according to other Embodiments 2 to 4 can also be used.

  For example, when the wavelength tunable light source 98 according to the second embodiment is used, a coupling optical system using a lens array or the like is arranged in parallel on one end face side of the wavelength tunable light source 98 and is transmitted in the same direction. An optical output 71 and a receiving optical output 72 are coupled to the optical fiber array. At this time, as shown in FIG. 6, the light extracted by the beam splitter may be input to the monitor.

  In the wavelength tunable light source 98 according to the third and fourth embodiments, light splitting by a beam splitter as shown in FIG. 6 is not required, and monitoring is not required.

<Embodiment 7>
FIG. 7 is a diagram illustrating an example of the configuration of the transmission / reception device 83 according to the seventh embodiment of the present invention.

  As shown in FIG. 7, the transmission / reception device 83 according to the seventh embodiment includes a modulator module 81, a receiver module 82, and a wavelength variable light source module 97.

  The modulator module 81 is a module in which a modulator such as a Mach-Zehnder interferometer and a modulator driver are modularized.

  The receiver module 82 is obtained by modularizing an optical 90-degree hybrid circuit that converts phase-modulated signal light into a light intensity signal, a photodiode that converts the light intensity signal into an electric signal, and an amplifier.

  The variable wavelength light source module 97 corresponds to the variable wavelength light source module 97 according to the sixth embodiment.

  The transmission light output 71 output from the wavelength tunable light source module 97 is phase-modulated by the modulator module 81 and then output to the outside as a transmission signal 73.

  The reception signal 74 received from the outside is input to the receiver module 82 together with the reception light output 72 output from the wavelength variable light source module 97, and interferes with the reception light output 72 at the receiver module 82. Thereafter, the interference light is photoelectrically converted by the photodiode of the receiver module 82. By performing such processing, the reception signal 74 is received.

  From the above, according to the seventh embodiment, the wavelength tunable light source module 97 can also be used as a light source module for transmission / reception. Therefore, the transmission / reception device 80 (two wavelength variable light source modules 91 according to the premise technology) ( The power consumption can be reduced as compared with FIG.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  10 DFB-LD, 11 DFB-LD array, 30 N × 1-MMI, 31 MMI input waveguide, 32 MMI output waveguide, 33 first input waveguide, 34 second input waveguide, 35 first Optical multiplexing circuit, 36 Second optical multiplexing circuit, 37 First output waveguide, 38 Second output waveguide, 39 Output waveguide for monitoring, 40 InP substrate, 41 InP lower cladding layer, 42 InGaAsP waveguide layer 43 InP upper cladding layer, 44 InP current blocking layer, 45 InGaAsP active layer, 46 InGaAsP contact layer, 50 optical phase modulator, 51 optical 90 degree hybrid circuit, 52 photodiode, 60 SOA, 61 first SOA, 62 Second SOA, 70 optical output for transmission, 71 optical output for transmission, 72 optical output for reception, 73 transmission signal, 4 Received signal, 75 Monitor light output, 80 Transmitter / receiver, 81 Modulator module, 82 Receiver module, 83 Transmitter / receiver, 90 Wavelength variable light source, 91 Wavelength variable light source module, 92 Coupling optical system, 93 Optical fiber, 94 Polarization Wave holding coupler, 95 beam splitter, 96 monitor, 97 wavelength variable light source module, 98 wavelength variable light source, 99 optical integrated device.

Claims (4)

A first input side and a first output side, one end of a plurality of first input waveguides is connected to the first input side, and a first output waveguide is provided on the first output side 1st optical multiplexing which combines and connects the 1st light input from each said 1st input waveguide, and outputs the said 1st light combined to said 1st output waveguide Circuit,
A second input side and a second output side are provided, one end of a plurality of second input waveguides is connected to the second input side, and a second output waveguide is provided to the second output side Second optical multiplexing that is connected and combines the second light input from each of the second input waveguides and outputs the combined second light to the second output waveguide Circuit,
A plurality of semiconductor lasers having one end connected to the other end of each first input waveguide and the other end connected to the other end of each second input waveguide, each capable of single mode oscillation at a different wavelength. When,
A first optical amplifier connected to the first output waveguide;
A second optical amplifier connected to the second output waveguide;
With
It said first output waveguide or said second output waveguides, wavelength variable light source you characterized by the plurality of presence includes a monitor output waveguide for monitoring the oscillation wavelength of the semiconductor laser of the output light When,
An optical integrated device comprising a modulator and a receiver,
The amplification factor of the first optical amplifier is larger than the amplification factor of the second optical amplifier,
The modulator is connected to the first optical amplifier of the tunable light source;
The optical integrated device, wherein the receiver is connected to the second optical amplifier of the variable wavelength light source. 2. The integrated optical device according to claim 1, wherein at least one of the first output waveguide and the second output waveguide is formed as a curved waveguide at an output end side. 3. The input end face and the output end face on the input side of the first optical multiplexing circuit or the second optical multiplexing circuit have a width W, and the first input waveguide or the second input waveguide When there are N waveguides (N is a natural number of 3 or more) and there are a plurality of the first output waveguides or the second output waveguides,
The first input waveguide or the second input waveguide is arranged symmetrically with respect to W / 2 of the input end face and at a spacing of W / N,
The first output waveguide or the second output waveguide is arranged symmetrically with respect to W / 2 of the output end face and at an interval of W / N, according to claim 1 or 2. The optical integrated device described. The first output waveguide and the second output waveguide are formed in an arc shape so that output ends of the first output waveguide and the second output waveguide are on the same end face side of the wavelength tunable light source. 4. The optical integrated device according to any one of items 1 to 3.

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