Optical Devices

Abstract

Provided is an optical device having a long life and high reliability. An optical device (200) according to one embodiment comprises at least one Mach-Zehnder (MZ) type modulator (201) and a redundant semiconductor optical amplifier (SOA) (202). The redundant SOA (202) is connected to the at least one MZ-type modulator (201) through a 2-input 2-output coupler (203). The redundant SOA (202) includes two SOAs (206a, 206b) arranged in parallel, and the two SOAs (206a, 206b) are arranged in two waveguides (205a, 205b), respectively, that are connected to the 2-input 2-output coupler (203). The redundant SOA (202) is configured to switch between the two SOAs (206a, 206b) to amplify light modulated or non-modulated by the at least one MZ-type modulator (201).

Description

[Technical Field]

[0001] The present disclosure relates to optical devices, and more particularly to optical devices with semiconductor amplifiers. [Background technology]

[0002] With the rapid increase in demand for communications, vigorous research is being conducted into increasing the capacity of communication networks. One key to achieving this is expanding the frequency bandwidth of optical modules that constitute optical transmitters and optical receivers. However, in optical modules and the optical devices implemented therein, there is generally a trade-off between frequency bandwidth and photoelectric conversion efficiency. That is, expanding the frequency bandwidth to increase communication capacity results in a corresponding decrease in photoelectric conversion efficiency. For example, in the case of an optical transmitter, the efficiency of converting an electrical signal into an optical signal decreases, resulting in a decrease in output optical power. Therefore, technology for integrating an optical amplifier into an optical transmitter is being actively studied (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6588851 Summary of the Invention

[0004] However, when integrating an optical amplifier and an optical circuit into a single optical device, the life of the optical amplifier determines the life of the entire optical device, which is a problem.

[0005] FIG. 1 is a diagram showing a schematic configuration of a general optical device. The optical device 100 in FIG. 1 includes a semiconductor optical amplifier (SOA) connected to a Mach-Zehnder (MZ) modulator 101. The MZ modulator 101 includes two arm waveguides 104a and 104b connecting a one-input, two-output coupler 102 and a two-input, one-output coupler 103, electrodes 105a and 105b provided on the two arm waveguides 104a and 104b, respectively, and a phase shifter 106 provided on at least one of the arm waveguides 104a and 104b. In FIG. 1, an electric signal is applied to the electrodes 15a and 15b so that the arm waveguide 104a provided with the electrode 105a serves as a Pos arm and the arm waveguide 104b provided with the electrode 15b serves as a Neg arm.

[0006] Light input from an input port of optical device 100 is branched into two by one-input, two-output coupler 102. Thereafter, light modulated by an electrical signal applied from electrode 105a while propagating through arm waveguide 104a and light modulated by an electrical signal applied from electrode 105b while propagating through arm waveguide 104b and whose phase has been adjusted by phase shifter 106 are combined by two-input, one-output coupler 103. The combined light is amplified by SOA 107 and then output from the output port of the optical device.

[0007] The optical device 100 configured as shown in FIG. 1 has a problem of low reliability because if the SOA breaks down, the entire optical device stops functioning, and the life of the SOA determines the life of the entire optical device.

[0008] The present disclosure has been made in view of such problems, and has as its object to provide an optical device that has a long life and high reliability.

[0009] To achieve this objective, an optical device according to one embodiment of the present disclosure includes at least one MZ modulator and a redundant SOA, the redundant SOA being connected to the at least one MZ modulator via a two-input, two-output coupler, and the redundant SOA includes two SOAs arranged in parallel, the two SOAs being arranged in two waveguides connected to the two-input, two-output coupler, respectively.

[0010] As described above, according to an embodiment of the present disclosure, it is possible to provide an optical device with a long life and high reliability. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a general optical device. [Figure 2] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. [Figure 3] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. [Figure 4] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. [Figure 5] FIG. 1A is a diagram showing a schematic configuration of an optical device according to an embodiment of the present disclosure, and FIG. 1B is a diagram showing a schematic configuration of an optical device of a reference example. [Figure 6] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. [Figure 7] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. [Figure 8] 1 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or similar reference numerals denote the same or similar elements, and repeated description may be omitted.

[0013] An optical device according to various embodiments of the present disclosure includes an MZ modulator (also simply referred to as an MZ modulator) and two redundant SOAs (also simply referred to as redundant SOAs) connected to the MZ modulator via a two-input, two-output coupler. The optical device according to one embodiment of the present disclosure further includes a variable optical attenuator (VOA). The MZ modulator, redundant SOA, and VOA are integrated on a waveguide substrate to form an optical device. In this disclosure, a coupler having M inputs and N outputs is referred to as an M-input N-output coupler or an M×N coupler, where M and N are integers. The coupler can be a directional coupler, a multimode interference (MMI) coupler, a branching waveguide, or a crossing waveguide.

[0014] According to the optical device configurations of various embodiments of the present disclosure, even if one of the redundant SOAs fails, it is possible to switch to the other, thereby extending the life of the optical device and increasing its reliability.

[0015] (Embodiment 1) Fig. 2 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 200 illustrated in Fig. 2 includes a 1-input 2-output coupler 102, a 2-input 2-output coupler 203, a 2-input 1-output coupler 204, arm waveguides 104a and 104b connecting the 1-input 2-output coupler 102 and the 2-input 2-output coupler 203, and arm waveguides 205a and 205b connecting the 2-input 2-output coupler 203 and the 2-input 1-output coupler 204.

[0016] The arm waveguide 104a includes an electrode 105a, and the arm waveguide 104b includes an electrode 105b and a phase shifter .

[0017] The arm waveguide 205a includes an SOA 206a, and the arm waveguide 205b includes an SOA 206a.

[0018] The one-input two-output coupler 102, the two-input two-output coupler 203, the arm waveguide 104a, the arm waveguide 104b, the electrode 105a, the electrode 105b, and the phase shifter 106 constitute an MZ modulator 201. The arm waveguide 104a and the arm waveguide 104b are configured to have the same length.

[0019] The two-input, two-output coupler 203, the two-input, one-output coupler 204, the arm waveguide 205a, the arm waveguide 205b, the SOA 206a, and the SOA 206b configure a redundant SOA 202. The arm waveguide 205a and the arm waveguide 205b are configured to have the same length. The redundant SOA 202 is configured such that a current or voltage is applied to the SOA 206a when amplifying light propagating through the arm waveguide 205a, and a current or voltage is applied to the SOA 206b when amplifying light propagating through the arm waveguide 205b.

[0020] Light input from an input port of the optical device 200 is branched into two by a one-input, two-output coupler 102. The light propagating through the arm waveguide 104a is modulated by an electrical signal applied from an electrode 105a. The light propagating through the arm waveguide 104b is modulated by an electrical signal applied from an electrode 105b, and then its phase is adjusted by a phase shifter 106. The light propagating through the arm waveguide 104a and the light propagating through the arm waveguide 104b enter a two-input, two-output coupler 203, where they are combined and branched into two lights again.

[0021] The two beams of light branched by the two-input two-output coupler 203 propagate through the arm waveguide 205a and the arm waveguide 205b, respectively. For example, a current or voltage can be applied to only one of the SOA 206a or the SOA 206b to amplify the light output from the output port of the optical device 200. The amplified light is output from the output port of the optical device 200 via the two-input one-output coupler 204. If one of the SOA 206a or the SOA 206b to which a current or voltage is being applied fails, the application of the current or voltage can be switched to the other of the SOA 206a or the SOA 206b to continue amplifying the light output from the output port of the optical device 200.

[0022] According to the configuration of the optical device of this embodiment, the life of the optical device is extended and the reliability is increased.

[0023] The configuration of this embodiment makes effective use of one of the two outputs of the two-input, two-output coupler 203 that constitutes the MZ modulator 201 when it is unused, thereby preventing an increase in the number of components of the optical device 200.

[0024] The optical device 200 has been described above with reference to FIG. 2 in which the redundant SOA amplifies the light modulated by the MZ modulator 201. However, the MZ modulator 201 may also be configured to modulate the light amplified by the redundant SOA.

[0025] (Embodiment 2) Fig. 3 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 300 illustrated in Fig. 3 differs from the optical device illustrated in Fig. 2 in that the MZ modulator modulates the light amplified by the redundant SOA, in that the redundant SOA amplifies the light modulated by the MZ modulator.

[0026] The optical device 300 shown in FIG. 3 includes a 1-input 2-output coupler 304, a 2-input 2-output coupler 303, a 2-input 1-output coupler 103, arm waveguides 205a and 205b connecting the 1-input 2-output coupler 304 and the 2-input 2-output coupler 303, and arm waveguides 104a and 104b connecting the 2-input 2-output coupler 303 and the 2-input 1-output coupler 103.

[0027] The arm waveguide 205a includes an SOA 206a, and the arm waveguide 205b includes an SOA 206b.

[0028] The arm waveguide 104a includes an electrode 105a, and the arm waveguide 104b includes an electrode 105b and a phase shifter .

[0029] The two-input two-output coupler 303, the two-input one-output coupler 103, the arm waveguide 104a, the arm waveguide 104b, the electrode 105b, the electrode 105b, and the phase shifter 106 constitute an MZ modulator 301. The configuration of the MZ modulator 301 is the same as the configuration of the MZ modulator 201 except for the number of inputs of the two-input two-output coupler 303 and the number of outputs of the two-input one-output coupler 103.

[0030] The 1-input 2-output coupler 304, the 2-input 2-output coupler 303, the arm waveguide 205a, the arm waveguide 205b, the SOA 206a, and the SOA 206b configure the redundant SOA 302. The configuration of the redundant SOA 302 is the same as the configuration of the redundant SOA 202 except for the number of inputs of the 1-input 2-output coupler 304 and the number of outputs of the 2-input 2-output coupler 303.

[0031] Light input from the input port of the optical device 300 is distributed equally to the arm waveguides 205a and 205b by the one-input, two-output coupler 304. For example, light can be amplified by applying a current or voltage to only one of the SOA 206a or 206b.

[0032] The light amplified by the redundant SOA 302, i.e., the two lights branched by the two-input, two-output coupler 303, propagate through the arm waveguides 104a and 104b, respectively, and then enter the two-input, one-output coupler 103, where they are combined and output from the output port of the optical device 300.

[0033] According to the configuration of the optical device 300 of this embodiment, if one of the SOA 206a or SOA 206b to which a current or voltage is applied fails, the application of the current or voltage can be switched to the other of the SOA 206a or SOA 206b, thereby allowing the amplification of the light output from the output port of the optical device 300 to continue.

[0034] In the redundant SA 301, the other of the SOA 206a or SOA 206b to which no current or voltage is applied absorbs light, and therefore the light propagating through the corresponding arm waveguide 205a or arm waveguide 205b is lost. In the configuration of the optical device 300 of this embodiment, when the power of light incident on the input port of the optical device 300 is large, the 3 dB loss in the 1-input 2-output coupler 304 and the characteristics of the redundant SOA 302 do not degrade the signal-to-noise ratio (OSNR) of the light in the optical device 300.

[0035] The optical device 300 of this embodiment functions as an attenuator when the application of current or voltage to the redundant SOA 302 is stopped, and therefore can also be used as a shutter having a function of shutting down light.

[0036] Like the optical device 200, the optical device 300 of this embodiment also has a longer life and higher reliability.

[0037] (Embodiment 3) 4 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 400 illustrated in FIG. 4 can amplify light without degrading the OSNR even when the power of light incident on the input port of the optical device 400 is low.

[0038] The optical device 400 in Fig. 4 includes a redundant SOA 402 connected to the MZ modulator 301. The redundant SOA 402 is obtained by replacing the 1-input 2-output coupler 303 with a 2-input 2-output coupler 404 in the configuration of the redundant SOA 302 in the optical device 300 in Fig. 3. The optical device 400 in Fig. 4 further includes an SOA path changeover switch 403 connected in front of the 2-input 2-output coupler 404.

[0039] The MZ type modulator 301 has the same configuration as the MZ type modulator 301 in the optical device 300 in FIG.

[0040] The two-input two-output coupler 404, the two-input two-output coupler 303, the arm waveguide 205a, the arm waveguide 205b, the SOA 206a, and the SOA 206b configure a redundant SOA 402. The configuration of the redundant SOA 402 is the same as the configuration of the redundant SOA 302 except for the number of inputs of the two-input two-output coupler 404.

[0041] The one-input, two-output coupler 405 , the two-input, two-output coupler 404 , the arm waveguide 406 a , the arm waveguide 406 b , and the phase shifter 407 configure the SOA path changeover switch 403 .

[0042] The one-input, two-output coupler 405 branches the light incident on the input port of the optical device 400 into the arm waveguide 406a and the arm waveguide 406b.

[0043] The arm waveguide 406a and the arm waveguide 406b are configured to have the same length.

[0044] The phase shifter 407 modulates the phase of the light propagating through the arm waveguide 404b in accordance with the applied current or voltage.

[0045] The two-input, two-output coupler 404 combines the arm waveguides 404a and 404b and distributes the combined light to the arm waveguides 205a and 205b of the redundant SOA 402. At this time, the proportion of light distributed to the arm waveguides 205a and 205b varies depending on the phase of the light propagating through the arm waveguide 404b. That is, the optical device 400 of this embodiment can control the proportion of light distributed to the arm waveguides 205a and 205b in the two-input, two-output coupler 404 by controlling the current or voltage applied to the phase shifter 407 of the SOA path switching switch 403. For example, when applying a current or voltage to the SOA 206a in the redundant SOA 402 to amplify light, the loss of light in the redundant SOA 402 can be reduced by increasing the proportion of light distributed to the arm waveguide 205a and decreasing the proportion of light distributed to the arm waveguide 205b.

[0046] As described above, the optical device 400 of this embodiment has a longer life span and higher reliability, similar to the optical device 300. Furthermore, the optical device 400 can amplify light without degrading the OSNR, even when the power of light incident on the input port of the optical device 400 is low.

[0047] (Embodiment 4) 5A is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 500 illustrated in FIG. 5 has a configuration in which a variable optical attenuator (VOA) is connected to the rear stage of the redundant SAO 202 of the optical device 200 in FIG. 2.

[0048] 5(a) in the optical device 500, the redundant SOA 502 is obtained by replacing the 2-input 1-output coupler 204 of the redundant SOA 202 in FIG. 2 with a 2-input 2-output coupler 503. The optical device 500 in FIG. 5(a) further includes a VOA 501 connected in a stage subsequent to the 2-input 2-output coupler 503.

[0049] The MZ type modulator 201 has the same configuration as the MZ type modulator 201 in the optical device 200 in FIG.

[0050] The two-input two-output coupler 203, the two-input two-output coupler 503, the arm waveguide 205a, the arm waveguide 205b, the SOA 206a, and the SOA 206b configure a redundant SOA 502. The configuration of the redundant SOA 502 is the same as the configuration of the redundant SOA 202, except for the number of outputs of the two-input two-output coupler 503.

[0051] A two-input, two-output coupler 503, a two-input, one-output coupler 504, arm waveguides 505a, 505b, and a VOA electrode 506 constitute a VOA 501. The arm waveguides 505a and 505b are configured to have the same length. In the VOA 501, the intensity of light output from the output port of the optical device 500 via the two-input, one-output coupler 504 changes depending on the current or voltage applied to the VOA electrode 506.

[0052] 5(b) is a diagram showing a schematic configuration of an optical device of a reference example. As shown in FIG. 5(b), when an SOA is interposed between the MZ modulator 201 and the VOA 501, an SOA (206b in FIG. 5(b)) is provided in a waveguide connecting one of the two outputs of the two-input / two-output coupler 203 to one of the two inputs of the two-input / two-output coupler, and the other of the two outputs of the two-input / two-output coupler 203 and the other of the two inputs of the two-input / two-output coupler are terminated. In the case of a configuration such as that shown in FIG. 5(b), the other of the two outputs of the two-input / two-output coupler 203 and the other of the two inputs of the two-input / two-output coupler are not terminated, but are connected by an arm waveguide 205a as shown in FIG. 5(a) to provide an SOA 206a, thereby configuring a redundant SOA without suppressing an increase in the number of components of the optical device.

[0053] The optical device 500 of this embodiment also has a longer life and higher reliability.

[0054] (Embodiment 5) Fig. 6 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 600 illustrated in Fig. 6 has a configuration in which the single MZ modulator 201 connected in front of the redundant SOA 502 of the optical device 500 in Fig. 5(a) is replaced with two MZ modulators 201a and 201b arranged in parallel.

[0055] The optical device of Figure 6 includes arm waveguides 605a and 605b connecting a 1-input 2-output coupler 602 and a 2-input 2-output coupler 203, an MZ type modulator 201a connected to the arm waveguide 605a, and an MZ type modulator 201b connected to the arm waveguide 605b.

[0056] The IQ modulator 601 is composed of the one-input two-output coupler 602, the two-input two-output coupler 203, the arm waveguides 605a and 605b, the MZ modulator 201a and the MZ modulator 201b.

[0057] As shown in FIG. 6, a redundant SOA 505 can be easily arranged after the two-input two-output coupler 203 on the output side of the IQ modulator 601, which extends the life of the optical device and increases its reliability.

[0058] In this embodiment, a redundant SOA is placed after the IQ modulator, but a redundant SOA can also be placed before the IQ modulator 601.

[0059] (Embodiment 6) Fig. 7 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 700 illustrated in Fig. 7 differs from the optical device 600 illustrated in Fig. 6 in that a redundant SOA is arranged in front of the IQ modulator.

[0060] The optical device 700 in Fig. 7 includes the redundant SOA 302 described with reference to Fig. 3, the VOA 501 described with reference to Fig. 5, arm waveguides 705a and 705b connecting the 2-input 2-output coupler 303 and the 2-input 2-output coupler 503, an MZ modulator 201a connected to the arm waveguide 705a, and an MZ modulator 201b connected to the arm waveguide 605b. The arm waveguides 705a and 705b are configured to have the same current flow.

[0061] Like the optical device 600, the configuration of the optical device 700 in FIG. 7 also increases the life span and reliability of the optical device.

[0062] (Embodiment 7) Fig. 8 is a diagram illustrating a schematic configuration of an optical device according to an embodiment of the present disclosure. The optical device 800 illustrated in Fig. 8 differs from the optical device 500 illustrated in Fig. 5(a) in that two IQ modulators 601a and 601b are arranged in parallel before the redundant SOA 502 in the optical device 500 illustrated in Fig. 5(a).

[0063] A DP-IQ (Dual Polarization In-phase Quadrature) modulator 801 is configured by a 1-input 2-output coupler 802, a 2-input 2-output polarization beam combiner (PBC) 803, arm waveguides 805a and 805b connecting the 1-input 2-output coupler 802 and the 2-input 2-output PBC 803, an IQ modulator 601a connected to the arm waveguide 805a, and an IQ modulator 601b and polarization rotator 804 connected to the arm waveguide 805b. The lengths of the beam waveguides 805a and 805b are configured to be equal. In this embodiment, a two-input, two-output polarization beam combiner (PBC) 803 functions as a two-input, two-output coupler that connects the MZ-type modulator and the redundant SOA.

[0064] Like the optical device 500, the configuration of the optical device 800 in FIG. 8 also increases the life span and reliability of the optical device. [Industrial Applicability]

[0065] According to the present disclosure, it is possible to provide an optical device with a longer life and high reliability. [Explanation of symbols]

[0066] 100, 200, 300, 400, 500, 600, 700, 800 Optical Devices 102, 304, 405, 802 1-input 2-output coupler 104a, 104b, 205a, 205b, 406a, 406b, 505a, 505b, 805a, 805b arm waveguides 105a, 105b electrode 106, 407 Phase Shifter 201, 301 MZ type modulator 202, 302, 402, 502 Redundant SOA 203, 303, 404, 503 2-input 2-output coupler 204, 504 2-input 1-output coupler 206a, 206b SOA 403 SOA Path Switch 501 Variable Optical Attenuator (VOA) 506 VOA electrode 507 Termination 601, 601a, 601b, 701 IQ Modulators 801 DP-IQ Modulator 803 2 input 2 output PCB 804 Polarization Rotator

Claims

1. An optical device, comprising: a redundant SOA including two semiconductor optical amplifiers (SOAs) arranged in parallel, the SOAs being individually controlled to be driven or stopped; at least one Mach-Zehnder (MZ) type modulator; an optical device comprising: a two-input, two-output coupler that connects the output waveguides of the two SOAs to two arm waveguides that constitute the MZ modulator;

2. 2. The optical device according to claim 1, wherein the redundant SOA is configured to switch which of the two SOAs to drive and amplify light before being modulated by the at least one MZ modulator.

3. 2. The optical device according to claim 1, wherein the redundant SOA functions as an optical shutter that shuts down optical input to the MZ modulator in response to a stop of driving.

4. The optical device of claim 1 , wherein the two-input, two-output coupler is configured to distribute light from the output waveguide to the two arm waveguides.

5. The optical device according to claim 4 , further comprising a changeover switch for controlling the proportion of light distributed to the output waveguide.

6. 2. The optical device according to claim 1, further comprising a variable optical attenuator (VOA) for controlling the attenuation of the output light of the MZ modulator.

7. 2. The optical device according to claim 1, wherein the number of said at least one MZ type modulator is two.

8. 2. The optical device according to claim 1, wherein the number of said at least one MZ type modulator is four, and said two-input two-output coupler is a two-input two-output polarization beam combiner.

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