JP2017083529A - Multi-wavelength modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-wavelength modulator that can be achieved with a planar waveguide circuit.SOLUTION: The multi-wavelength modulator comprises: first and second semiconductor optical waveguides (12, 13); a 3dB coupler (10) that splits input light into the first and second semiconductor optical waveguides (12, 13) and combines the light from the first and second semiconductor optical waveguides (12, 13) to be outputted; third and fourth semiconductor optical waveguides (14a1, 14b1) respectively including phase shifters (17a1, 17b1), and having one end connected to a loop mirror (15a1); and a pair of splitters (16a1, 16b1) having the same wavelength selectivity, provided between the other end of the third semiconductor optical waveguide (14a1) and the first semiconductor optical waveguide (12), and between the other end of the fourth semiconductor optical waveguide (14b1) and the second semiconductor optical waveguide (13). A plural sets of the third and fourth semiconductor optical waveguides (14a1, 14b1) including the phase shifters and the pairs of splitters (16a1, 16b1) are provided corresponding to a plurality of different wavelength channels.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor modulator that modulates the intensity of an optical signal in optical fiber communication or the like, and more particularly, to a multiwavelength modulator that can independently modulate input light from a multiwavelength light source for each wavelength.

  As a conventional optical modulator used in optical fiber communication or the like, particularly as an optical modulator that can be mounted on a silicon substrate as a planar lightwave circuit (PLC), for example, the optical modulation disclosed in Patent Document 1 There is a vessel. This optical modulator performs intensity modulation of input light using a semiconductor Mach-Zehnder interferometer (MZI).

  FIG. 5 is a diagram showing a schematic configuration of the Mach-Zehnder modulator 100. In FIG. 5, reference numerals 101 and 102 denote 3 dB couplers, which couple two arm waveguides 103 and 104 constituting a Mach-Zehnder interferometer. Reference numerals 105 and 106 denote phase shifters that perform phase modulation of light propagating through the waveguide by partially applying a voltage to the arm waveguides 103 and 104. If the voltage applied to the phase shifters 105 and 106 is adjusted so that the phase difference of the light propagating through the two arm waveguides is π (or (2n + 1) π: n is an arbitrary integer), 3 dB coupling The output light combined by the device 102 becomes zero. On the other hand, when the phase difference of light is 0 (or 2πn: n is an arbitrary integer), strong output light can be obtained. In this way, the intensity of light can be modulated by adjusting the voltage applied to the phase shifters 105 and 106.

  In the case of using the Mach-Zehnder modulator 100 shown in FIG. 5 in wavelength division multiplexing, normally, intensity modulation is performed simultaneously on a plurality of wavelengths. On the other hand, when optical signal modulation is performed separately for each wavelength, it is necessary to have a duplexer for dividing the light from the multiwavelength light source into individual wavelength channels and the same number of Mach-Zehnder modulators as the number of wavelength channels. It becomes. Therefore, since the chip size increases and the cost increases with the increase in the number of wavelength channels, a multiwavelength modulator using a planar waveguide circuit capable of intensity modulation for each wavelength has not yet been realized.

  FIG. 6 is an image diagram when a multi-wavelength modulator is configured using the Mach-Zehnder modulator of FIG. In FIG. 6, 107a, 107b,... Are a plurality of ring resonators arranged along the input waveguide 108 or the output waveguide 109, which selectively couple with a specific wavelength and separate. That is, the ring resonators 107a, 107b... Function as duplexers. The wavelength multiplexed signal propagating through the input waveguide 108 is separated into respective wavelength channels by ring resonators 107a and 107b, and intensity-modulated by Mach-Zehnder modulators 100a, 100b... Provided for each wavelength channel. It is output to the output waveguide 109 via 107a and 107b.

  As shown in FIG. 6, when a multi-wavelength modulator is configured using a Mach-Zehnder modulator, a single Mach-Zehnder modulator itself requires a considerable chip area, so that the number of chips increases as the number of channels increases. The area increases, which causes an increase in cost, and the realization thereof involves many difficulties.

  Accordingly, there is a need for a semiconductor multiwavelength modulator that can individually modulate a wavelength multiplexed signal for each wavelength with a small chip area.

JP 2014-10189 A

  It is an object of the present invention to provide a multi-wavelength modulator having a novel structure that can perform signal modulation for each wavelength channel in wavelength division multiplex transmission and can be implemented as a planar waveguide.

  In order to solve the above-described problem, in one aspect of the present invention, input light is branched into the first and second semiconductor optical waveguides and the first and second semiconductor optical waveguides, and the first and second semiconductor optical waveguides are branched. A 3 dB coupler for combining and outputting light from the semiconductor optical waveguides, third and fourth semiconductor optical waveguides each having a phase shifter and having one end connected to a loop mirror, and the third semiconductor optical waveguide A pair of components having the same wavelength selectivity provided between the other end of the waveguide and the first semiconductor optical waveguide, and between the other end of the fourth semiconductor optical waveguide and the second semiconductor optical waveguide, respectively. A plurality of sets of the third and fourth semiconductor optical waveguides and the pair of demultiplexers each including the phase shifter corresponding to a plurality of different wavelength channels. A modulator is provided.

  In the multi-wavelength modulator according to the above-described aspect, each of the pair of duplexers may be configured by a ring resonator.

  In the multiwavelength modulator according to the above-described aspect, a multiwavelength light source may be connected to an input side terminal of the 3 dB coupler.

  In the multi-wavelength modulator according to the above-described aspect, a high-speed modulation signal may be applied to the phase shifter.

  In the multiwavelength modulator according to the above aspect, the phase shifter includes a part of the third or fourth waveguide formed of i-type silicon, a p-type silicon layer formed on both sides thereof, and an n-type. A PIN type phase shifter formed by a silicon layer may be used.

  In the multi-wavelength modulator according to the above aspect, the loop mirror may be connected to the third or fourth waveguide through an MMI coupler.

  According to the multiwavelength modulator of the present invention, it is possible to obtain a semiconductor waveguide type multiwavelength modulator capable of optically modulating multi-wavelength input light for each wavelength channel. In this case, the length of the phase shifter for obtaining the phase shift amount necessary for the modulation can be greatly shortened by using reflection, so that the multi-wavelength modulator can be realized with a small chip area. Manufacturing costs are reduced.

The figure which shows the operation | movement principle of the optical modulator using a Michelson interferometer. The figure which shows schematic structure of the multiwavelength modulator which concerns on one Embodiment of this invention. The figure which shows other embodiment of a phase shifter. (A) is a figure which shows the optical wiring board for communication between LSI chips incorporating the multiwavelength modulator which concerns on one Embodiment of this invention, (b) is a partially expanded view of (a). The figure which shows the structure of a Mach-Zehnder modulator. The image figure in the case of comprising a multi-wavelength modulator using a Mach-Zehnder modulator.

  In the present invention, a Michelson interferometer is used to modulate the intensity of light. FIG. 1 is a diagram for explaining light intensity modulation using a Michelson interferometer. The input waveguide is branched into two arm waveguides 2 and 3 by a 3 dB coupler 1, and loop mirrors 4 and 5 as reflectors are provided at the end of each arm waveguide. Therefore, the propagation light reflected by the loop mirrors 4 and 5 propagates again through the arm waveguides 2 and 3 and is combined by the 3 dB coupler 1 and output. Reference numerals 6 and 7 denote phase shifters for performing phase modulation on the light propagating through the arm waveguides 2 and 3. The intensity modulation of the light is performed by the phase shifter 6, so that the phase of the light traveling from the arm waveguide 2 toward the 3 dB coupler 1 and the phase of the light from the arm waveguide 3 become a phase difference 0 or a phase difference π. This is realized by controlling 7.

  As shown in FIG. 1, in the optical modulator using the Mach-Zehnder interferometer, the light reflected by the loop mirrors 4 and 5 passes through the phase shifters 6 and 7 again, so that the phase shift effect by the phase shifters 6 and 7 is Increase. Therefore, the length of the phase shifter for obtaining a necessary phase shift amount can be shortened compared with the case of the Mach-Zehnder modulator.

  FIG. 2 is a diagram showing a schematic configuration of a semiconductor waveguide type multi-wavelength modulator according to an embodiment of the present invention configured by using a Michelson interferometer. In the embodiments described below, only waveguides are referred to, but these can be constituted by, for example, planar optical waveguides mounted on a silicon substrate. In FIG. 1, reference numeral 10 denotes a 3 dB coupler, which splits light propagating through the input optical waveguide 11 into the first and second optical waveguides 12 and 13 and propagates the first and second optical waveguides. The light from the waveguides 12 and 13 is combined and output to the output waveguide 18.

  Reference numerals 16a1 to 16a4 denote ring resonators that constitute a duplexer disposed along the first waveguide 12, and have a function of selectively coupling and separating light with wavelengths λ1 to λ4. Similar to the ring resonators 16a1-16a4, 16b1-16b4 has a function of selectively coupling and separating light with wavelengths λ1-λ4. In the illustrated example, four pairs of ring resonators 16a1 and 16b1 are provided, but the present invention is not limited to this, and a necessary number is provided according to the number of channels. The other ends of the first and second optical waveguides 12 and 13 have a non-reflection termination structure such as a narrow taper.

  Reference numerals 14a1 and 14b1 denote a pair of arm waveguides that are optically connected to the pair of ring resonators 16a1 and 16b1, and correspond to the arm waveguides 2 and 3 in the Michelson interferometer of FIG. A pair of arm waveguides 14a2, 14b2,... 14a4, 14b4 is provided for each ring resonator pair. Further, loop mirrors 15a1, 15b1,... 15a4, 15b4 are connected to the other ends of the respective arm waveguides. Further, each arm waveguide includes phase shifters 17a1, 17b1,... 17a4, 17b4.

  As is clear from comparing the multi-wavelength modulator of FIG. 2 with the Michelson interferometer of FIG. 1, the multi-wavelength modulator of this embodiment includes a pair of arm waveguides having a reflector connected to the end. A number corresponding to the number of channels is arranged in parallel, and each arm waveguide is coupled by a 3 dB coupler 10 to operate as a Michelson interferometer. Light intensity modulation is performed by adjusting voltage application to the pair of phase shifters 17a1-17a4, 17b1-17b4. Actually, optical modulation for each wavelength channel is performed by applying individual high-frequency modulation signals to each phase shifter pair corresponding to the wavelengths λ1, λ2,. The individually modulated wavelengths λ1, λ2,... Λ4 are wavelength-multiplexed by the 3 dB coupler 10 and output from the output waveguide 18.

  As described above, in the multi-wavelength modulator according to the embodiment of the present invention, the light propagating through the arm waveguide is reciprocated using the loop mirror as the reflector, so that a necessary phase difference is formed. Therefore, the lengths of the phase shifters 17a1-17a4 and 17b1-b4 can be sufficiently shortened. Furthermore, since the input / output waveguide is coupled by one 3 dB coupler 10 to form a Michelson interferometer, the chip area is reduced, and a planar waveguide circuit can be configured. Further, the manufacturing cost is reduced due to the reduction of the chip area.

  FIG. 3 is a diagram showing another embodiment of the present invention, and shows a state in which the loop mirror 15 is connected to the arm waveguide 14 via the MMI coupler 20. In this embodiment, the phase shifter is formed of a p-type layer 21 and an n-type layer 22 that are formed with the arm waveguide 14 interposed therebetween. The p-type layer 21 and the n-type layer 22 form a PIN structure with the arm waveguide 14 made of i-type silicon interposed therebetween. This PIN type phase shifter is a kind of optical shifter, and changes the refractive index of the arm waveguide 14 by a carrier dispersion effect generated by applying a voltage between the p layer and the n layer.

  FIG. 4A is a diagram showing a circuit that realizes communication between LSI chips using a wavelength-division multiplexed broadband optical wiring, using the multi-wavelength modulator according to the embodiment of the present invention. In FIG. 4A, reference numeral 30 denotes a planar waveguide circuit board that performs optical communication between the LSI chip A and the LSI chip B. Reference numeral 32 denotes a multi-wavelength light source such as a DFB laser array. In FIG. 4A, the light source 32 is shown as an on-chip integrated element, but collective input from the off-chip integrated element is realistic from the viewpoint of cost and ease of manufacture. Reference numeral 34 denotes a semiconductor waveguide for carrying light from the multi-wavelength light source 32 to the multi-wavelength modulators 36 and 38 according to the embodiment of the present invention. The multi-wavelength modulators 36, 36... Receive a high-frequency modulation signal from the LSI chip A, and the multi-wavelength modulators 38, 38.

  The configuration of each of the multi-wavelength modulators 36 and 38 is shown in FIG. The configuration and operation of the multi-wavelength modulator are the same as the configuration and operation of the multi-wavelength modulator shown in FIG.

  In FIG. 4A, reference numeral 40 denotes a light receiver that constitutes the output unit of the multi-wavelength modulator 36, and has a wavelength demultiplexing function. The light receiver 40 transmits a light reception signal to the LSI chip B. Reference numeral 42 denotes a light receiver that constitutes the output unit of the multi-wavelength modulator 38, which has a wavelength demultiplexing function like the light receiver 40, but transmits a light reception signal to the LSI chip A.

  In the circuit of FIG. 4, when a multiplexed signal is transmitted from the LSI chip A to the LSI chip B, a plurality of channels of modulated signals are transmitted to the multi-wavelength modulators 36, 36. Are modulated for each channel, and the multiplexed signal light after modulation is transmitted to the LSI chip B through the light receivers 40, 40. Conversely, when a multiplexed signal is transmitted from the LSI chip B to the LSI chip A, a modulated signal of a plurality of channels is transmitted to the multi-wavelength modulators 38, 38,. And the multiplexed signal light after modulation is transmitted to the LSI chip A through the light receivers 42, 42. As a result, communication between LSI chips can be realized by wavelength-multiplexed broadband optical wiring.

DESCRIPTION OF SYMBOLS 10 3dB coupler 11 Input waveguide 12 Branch waveguide 13 Branch waveguide 14a1, 14a2 ... Arm waveguide 14b1, 14b2 ... Arm waveguide 15a1, 15a2 ... Loop mirror 15b1, 15b2 ... Loop Mirror 16a1, 16a2 ... Ring resonator 16b1, 16b2 ... Ring resonator 17a1, 17a2 ... Phase shifter 17b1, 17b2 ... Phase shifter 18 Waveguide for output

Claims (6)

First and second semiconductor optical waveguides;
A 3 dB coupler for branching input light into the first and second semiconductor optical waveguides, and combining and outputting the light from the first and second semiconductor optical waveguides;
Third and fourth semiconductor optical waveguides each having a phase shifter and having one end connected to a loop mirror;
Same wavelength selection provided between the other end of the third semiconductor optical waveguide and the first semiconductor optical waveguide, and between the other end of the fourth semiconductor optical waveguide and the second semiconductor optical waveguide, respectively. A pair of duplexers having characteristics,
The third and fourth semiconductor optical waveguides including the phase shifter and the pair of duplexers are multi-wavelength modulators in which a plurality of sets are provided corresponding to a plurality of different wavelength channels.   The multi-wavelength modulator according to claim 1, wherein each of the pair of duplexers is configured by a ring resonator.   3. The multi-wavelength modulator according to claim 1, wherein a multi-wavelength light source is connected to an input side terminal of the 3 dB coupler.   4. The multi-wavelength modulator according to claim 1, wherein a high-speed modulation signal is applied to the phase shifter. 5.   5. The multi-wavelength modulator according to claim 1, wherein the phase shifter is formed on a part of the third or fourth waveguide formed of i-type silicon and on both sides thereof. A multi-wavelength modulator, which is a PIN phase shifter formed by a p-type silicon layer and an n-type silicon layer.   6. The multi-wavelength modulator according to claim 1, wherein the loop mirror is connected to the third or fourth waveguide through an MMI coupler. 7.

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