JPH07162394A - Semiconductor optical signal output device - Google Patents

Abstract

PURPOSE:To provide a high speed, highly precise and highly efficient semiconductor optical signal output device in a time-divisional multiplex optical signal output device. CONSTITUTION:A light source 11, an optical branching circuit 12, absorbing-type optical modulators 14A, 14B and 14C, the optical amplifier 15 of loss compensation, optical waveguide delay lines 13A-13F and an optical multiplexing circuit 16 are integrated on a semiconductor substrate 100. Micro wave delay lines for absorbing-type optical modulator driving 20A, 20B and 20C are added on the semi-insulating semiconductor substrate 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor time division multiplexing optical signal output device which is a signal output device for ultra high speed and large capacity optical communication or an optical soliton signal output device for long distance transmission.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventionally proposed time-division multiplexing optical signal output device (ofC / IO of 1993).
OC Technical Digest Th-1
3). In the figure, 1 is an input part of an optical short pulse, 2 is an optical branch circuit, 3 is an optical fiber delay line, 4 is an external modulator element, 5 is an optical fiber, and 6 is an optical merging circuit. The operation of the time division multiplexing optical signal output device is as follows. An optical pulse having a constant cycle, which is an input signal, is branched into n by a branch circuit 2 and is guided to an external modulator element 4 via an optical fiber delay line 3 having a delay time difference of 1 / n of the cycle of the optical pulse. Here, each optical fiber is an external modulator element 4
It is modulated by, is merged by the optical merging circuit 6, and is then output. That is, it is possible to output a time division multiplexed optical signal having a density n times the signal density obtained by the external modulator element 4.

However, in this conventional time-division multiplexed optical signal output device, the optical fiber delay line 3 is required to have a highly accurate delay time difference. For example 50 Gb / s
When obtaining the output signal of, the pulse interval of the output light is 20p
If s is required to be 5%, the permissible error for the delay time is 1 ps. There is a problem that it is practically impossible to obtain such high precision by adjusting the length of the optical fiber.

Furthermore, not only high-precision assembly is required at the connection point of the optical fiber connecting each element, but a connection loss of about 5 dB per connection point, a total of about 30 dB is expected, and the optical short pulse generation light source There is a drawback that the output is not used effectively.

[0005]

With the conventional time-division multiplexed optical signal output device as described above, it is technically difficult to adjust the length of the optical fiber delay line 3 with high precision. Since there are many connection points between the element and the optical fiber, there are many places where high precision (about 1 μm) is required for assembly of the device, and the optical power emitted from the optical short pulse generation light source cannot be effectively used. there were.

Therefore, it can be easily inferred that the optical waveguide delay line can be used in place of the optical fiber delay line to achieve high-precision assembly. However, when the optical waveguide delay line is actually incorporated in the semiconductor optical integrated circuit. Since there are the following problems in constructing the time division multiplexed optical signal output device, there has been no realization example. (1) If the optical waveguide delay line is composed of a semiconductor, the absorption loss in the waveguide is different, so that the output of the optical pulse varies. (2) Since the optical modulator is arranged near the center of the semiconductor optical integrated circuit board, it is difficult to supply a high-speed electric signal to the optical modulator with low crosstalk. (3) In order to mount the optical waveguide delay line and the optical modulator in a small-sized semiconductor optical integrated circuit, it is necessary to dispose the optical waveguide delay line before and after the optical modulator. There is a time lag before the signal reaches each optical modulator, and it is necessary to adjust this at the electric signal input side that feeds each optical modulator, which complicates control.

In view of such circumstances, it is an object of the present invention to provide a semiconductor optical signal output device which is a time division multiplexed optical signal output device which is high speed, high precision, high efficiency and easy to drive electrically. .

[0008]

To achieve the above object, the structure of the present invention is (1) an optical short pulse generating light source, and an optical branching circuit for branching the output light from this light source into N optical waveguides.
N optical waveguide delay lines of different lengths provided so as to have a delay time difference corresponding to 1 / N of the optical pulse period derived from the optical branch circuit and output from the optical short pulse generating light source, N absorption type optical modulators and N optical amplifiers interposed on the N optical waveguide delay lines, and an optical merging circuit that collectively outputs the N optical waveguide delay lines. Characterized by being integrated on a semiconductor substrate,

(2) In the semiconductor optical signal output device described in (1) above, the semiconductor substrate is semi-insulating and is formed on the semiconductor substrate as a power supply circuit for supplying electric signals to N absorption type optical modulators. Has N microwave delay lines,
Moreover, the delay time of the electric signal in the N microwave delay lines is the same as the delay time from the input of the drive signal of the optical short pulse generating light source to the arrival of the absorption type optical modulator to which the microwave delay lines are connected. It is characterized by

[0010]

The present invention having the above construction operates as a time division multiplexed optical signal output device. That is, the optical pulse output from the optical short pulse generating light source is branched into N lines by the optical branch circuit, and the branched pulse light is guided to the optical merging circuit by the optical waveguide delay line passing through the absorption type optical modulator and the optical amplifier, respectively. The branched pulse lights branched into N lines by the optical branch circuit are modulated by the absorption type optical modulator, respectively, and are output by the optical waveguide delay line at a delay time difference of 1 / N time per pulse period. Since they are combined by the optical combining circuit, the pulsed light is output as an N-multiplexed modulated signal. On the other hand, the modulation bit rate of the electric signal for driving the absorption type optical modulator is the speed before N-multiplexing by the above-mentioned configuration,
That is, the bit rate is the same as that of the optical pulse output from the optical short pulse generating light source, and the band limitation by the electric signal is relaxed. Further, in the present invention, since the optical waveguide delay line integrally formed on the semiconductor substrate is used, an optical delay line having a precise delay time difference can be easily realized. Also,
An optical amplifier is placed between each optical waveguide delay line to overcome the disadvantage of the semiconductor optical waveguide delay line, that is, the output difference between pulses caused by a rather large waveguide loss, and the output pulse intensity is adjusted uniformly. Became possible. Further, in the present invention, since the microwave delay line can be formed on the same semi-insulating semiconductor substrate, the delay time required for the electric signal for driving the absorption type optical modulators in parallel depends on the microwave delay line. Since it can be set in advance and all the absorption type optical modulator driving signals have the same phase relationship as the driving electric signals of the optical short pulse generating light source, the control is greatly simplified.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a semiconductor optical signal output device according to the present invention in a semi-insulating semiconductor substrate, showing an optical short pulse generating light source, an optical branch circuit, three sets of optical waveguide delay lines, an absorption type optical modulator and a waveguide loss. Three adjustment optical amplifiers each, an optical merging circuit, an output optical amplifier, three microwave delay lines that are AC feeding lines of an absorption type optical modulator, an impedance matching thin film resistance element, and a microwave bypass capacitor element. Three
It is a block diagram when it implement | achieves using a semiconductor monolithic element which consists of pieces, 10 is a semi-insulating semiconductor substrate,
11 is an optical short pulse generating light source, 12 is an optical branch circuit, 13A
13A to 13F are optical waveguide delay lines, 14A to 14C are absorption type optical modulators, 15 is a waveguide loss adjusting optical amplifier, 16 is an optical merging circuit, 17 is an output optical amplifier, and 18A to 18E are connection optical waveguides. 20A, 20B and 20C are microwave delay lines, 21 is an impedance matching thin film resistance element, and 22 is a microwave bypass capacitor element.

FIG. 2 is a conceptual diagram showing an example of arrangement of elements constituting a semiconductor monolithic element in one embodiment of the semiconductor optical signal output device of this embodiment shown in FIG. In FIG. 2, 111 is the light short pulse generation light source 11 in FIG.
111A is an electrode of a DFB laser which constitutes this light short pulse generation light source, 111B is an electrode of an absorption type optical modulator for forming a short light pulse, and 111C is a drive signal to the absorption type optical modulator. A coplanar microwave line for supplying power, 111D is a thin film resistor that constitutes a thin film resistance element for impedance matching, and 111E is an insulator that constitutes a capacitor element for microwave bypass, and is a modulator for obtaining a short optical pulse. , And a matching element for AC microwave.

The three optical waveguide delay lines from the optical branch circuit are connected to the absorption type optical modulator electrode 114 corresponding to the absorption type optical modulator 14A shown in FIG. 1 is a coplanar microwave delay line 120A corresponding to the delay line 20A shown in FIG. 1, a thin film resistor 121 constituting an impedance matching thin film resistance element corresponding to 21 of FIG. 1, and a microwave bypass corresponding to 22 of FIG. The insulator 122 that constitutes the capacitor element is connected.
Further, the electrode 115 of the optical amplifier for adjusting the waveguide loss corresponding to the optical amplifier 15 shown in FIG. 1 is arranged, and the optical waveguide delay line 13D
Is provided. The optical merging circuit is connected to the electrode 117 of the output optical amplifier shown by 17 in FIG. 1 via the connecting optical waveguide 18E. In the embodiment of FIG. 2, a series structure of a DFB laser and an absorption type optical modulator was used as the light short pulse generation light source, but other than this, as the light short pulse generation light source,
Various semiconductor light short pulse generating light sources such as a mode-lock laser and a gain switch laser can be used.

Next, the operation of the apparatus in the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 3 is a diagram for explaining the timing of the optical signal and the electric signal in each part of FIG. In the figure, the symbol with a suffix to T indicates the time at the center of the pulse, the symbol with an arrow indicates the time between pulses, and the numbers 1 and 0 indicate the modulated signal. (A) is fGb input to drive the light short pulse generating light source 11.
/ S electric signals, (b), (c), and (d) represent fGb / s NRZ electric signals input to the microwave delay lines 20A, 20B, and 20C, respectively, and each signal has the same phase. There is a relationship, and the interval is 1 / fs.
(E), (i), (m) are optical waveguide delay line 1 respectively
Optical pulses input to the absorption type optical modulators 14A, 14B and 14C after passing through 3A, 13B and 13C, respectively.
(F), (j), (n) are microwave delay lines 20A,
After passing through 20B and 20C, the absorption type optical modulator 14
NRZ electrical signal input to A, 14B, 14C,
(G), (k), and (o) are absorption type optical modulators 14, respectively.
Optical pulse output from A, 14B, and 14C, (h),
(L) and (p) are optical waveguide delay lines 13D and 13D, respectively.
E and 13F show the optical pulse that is incident on the optical combining circuit 16, and (q) shows the optical pulse that passes through the output optical amplifier 17 and is output from the element.

Here, each absorption type optical modulator 14A,
In order to accurately modulate the optical pulse input at 14B and 14C, the phase of the optical pulse and the phase of the electric signal must match. Therefore, each optical waveguide delay line 13A,
13B and 13C and microwave delay lines 20A and 20B,
The delay time at 20C is determined as follows. (1) Input to absorption type optical modulator 14A (delay time from input of electric signal for driving optical short pulse generation light source 11 to emission of optical short pulse) + (connection optical waveguide 18D and optical branch circuit 12) Time when optical pulse passes through optical waveguide delay line 13A) = (microwave delay line 20A
NRZ electrical signal) = TA1-TP1 (2) Input to absorption optical modulator 14B (delay time from the electrical signal input for driving the optical short pulse generation light source 11 to the emission of the optical short pulse) + (Time when the optical pulse passes through the connecting optical waveguide 18D, the optical branching circuit 12, and the optical waveguide delay line 13B) = (microwave delay line 20B
NRZ electric signal passing time) = TB1-TP1 (3) Input to the absorption type optical modulator 14C (delay time from the electric signal input for driving the optical short pulse generating light source 11 to the emission of the optical short pulse) + (Time for the optical pulse to pass through the connecting optical waveguide 18D, the optical branching circuit 12, and the optical waveguide delay line 13C) = (microwave delay line 20C
(TC) -TC1 (4) The delay time difference between the optical waveguide delay lines for performing the time division multiplexing of the optical pulse. In the optical waveguide delay lines 13A, 13B, 13C and 13D, (Delay time by 13B) + (Delay time by 13E)]-[(Delay time by 13A) + (Delay time by 13D)] = [(Delay time by 13C) + (13F
Delay time)] − [(13B delay time) +
(Delay time due to 13E)] = (TE1-TP1)-
(TD1-TP1) = (TF1-TP1)-(TE1-
TP1) = 1 / 3f (sec) By satisfying the above relationship, the time division multiplexing operation of the optical pulse by the parallel electric signal input having the same phase as the electric signal for generating the optical short pulse becomes possible. The output light pulse is delayed by the passage of the optical merging circuit 16 and the connecting optical waveguide 18E and is output at the timing shown in (q). Here, each time is (TO1-TD1) = (TO2-TE1) = (TO3-
TF1) = (time for the optical pulse to pass through the optical merging circuit 16 and the connecting optical waveguide 18E).

Thus, according to this embodiment using a semi-insulating semiconductor substrate, a light source for generating an optical short pulse, an optical branch circuit, an absorption type optical modulator, an optical amplifier, an optical waveguide delay line, and a microwave delay are provided on the same semiconductor substrate. Since the line, the impedance matching thin-film resistance element, and the microwave bypass capacitor element are integrally formed with high precision, the following effects are achieved. (1) Since the optical waveguide delay line integrally formed in the portion where strict control of the delay time difference is required is used, a highly accurate element can be realized without adjustment. (2) Wiring for driving the optical modulator Parallel high-speed electrical signal wiring can be easily performed with low crosstalk. (3) It is possible to feed power directly from the microwave line to the absorption-type optical modulator electrode section, and as a result of eliminating stray capacitance due to the wiring bonding pad that has limited the operating speed of the absorption-type optical modulator, Significant speedup has become possible. (4) Since the delay time required for the electric signals for driving the absorption type optical modulators in parallel can be set in advance by the microwave delay line, all the absorption type optical modulator driving signals are optical short pulse generation light sources. It is possible to have the same phase relationship as the driving electric signal of, and the control can be greatly simplified. (5) Since there is only one connection point with the optical fiber, the efficiency is high, and there are few assembling points that require high accuracy. (6) The difference in the optical absorption loss caused by the difference in the length of the optical waveguide delay line passing through is canceled by adjusting the amplification degree of the optical amplifier inserted in each optical waveguide delay line, and the output pulse intensity is made uniform. It has become possible.

The above description with reference to FIGS. 1 and 2 is based on the semi-insulating semiconductor substrate, but the present invention can be applied to semiconductor substrates other than the semi-insulating semiconductor substrate, and the pattern as shown in FIG. Thus, a semiconductor optical signal output device can be obtained. Regarding a semi-insulating semiconductor substrate or a semiconductor substrate coated with an insulating layer, the microwave circuit and the optical circuit could be directly integrated, but otherwise the operating speed of the absorption type optical modulator is limited. Although a wiring bonding pad is required, the shape of the electrodes 111F and 123 is preferably the square or circle shown in the figure in order to reduce the stray capacitance as much as possible.

[0018]

As described above, the semiconductor optical signal output device of the present invention operates as a semiconductor time-division multiplexed optical signal output device, and (1) is integrated with a portion requiring strict control of delay time difference. Since the formed optical waveguide delay line is used, a highly accurate element can be realized without adjustment. (2) Since there is only one connection point with the optical fiber, the efficiency is high and the number of assembling points requiring high accuracy is small. (3) The difference in the optical absorption loss caused by the difference in the lengths of the optical waveguide delay lines passing therethrough is canceled by adjusting the amplification degree of the optical amplifier inserted in each optical waveguide delay line, and the output pulse intensity is made uniform. It has become possible.

Furthermore, when a semi-insulating semiconductor substrate is used, the following effects are also obtained. (4) Wiring for driving the optical modulator Parallel high-speed electrical signal wiring can be easily performed with low crosstalk. (5) It is possible to feed power directly from the microwave line to the absorption optical modulator electrode section, and as a result of eliminating stray capacitance due to the wiring bonding pad that has previously limited the operation speed of the absorption optical modulator, Significant speedup has become possible. (6) Since the delay time required for the electric signals for driving the absorption type optical modulators in parallel can be set in advance by the microwave delay line, all the absorption type optical modulator driving signals are optical short pulse generation light sources. It is possible to have the same phase relationship as the driving electric signal of, and the control can be greatly simplified.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a semiconductor optical signal output device according to an embodiment of the invention.

FIG. 2 is a conceptual diagram showing an arrangement pattern of elements constituting a semiconductor monolithic element of a semi-insulating semiconductor optical signal output device according to an example of the present invention.

FIG. 3 is a diagram for explaining timings of an optical signal and an electric signal in each part of FIG.

FIG. 4 is a conceptual diagram showing an arrangement pattern of a semiconductor optical signal output device other than a semi-insulating type according to an embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example of a conventionally proposed time division multiplexing optical signal output device.

[Explanation of symbols]

1 Optical Short Pulse Input Section 2 Optical Branch Circuit 3 Optical Fiber Delay Line 4 External Modulator Element 5 Optical Fiber 6 Optical Merging Circuit 10 Semi-Insulating Semiconductor Substrate 11 Optical Short Pulse Generation Light Source 12 Optical Branch Circuit 13A-13F Optical Waveguide Delay Line 14A to 14C Absorption type optical modulator 15 Waveguide loss adjusting optical amplifier 16 Optical merging circuit 17 is an output optical amplifier 18A to 18E Connection optical waveguide 20A to 20C Microwave delay line 21 Impedance matching thin film resistance element 22 Micro Capacitor element for wave bypass 111A Electrode of DFB laser constituting light source for generating short optical pulse 111B Electrode of absorption type optical modulator constituting light source for generating short optical pulse 111C Coplanar microwave line 111D Thin film resistor 111E Insulator 111F Electrode 114 Electrode 115 of absorption type optical modulator For adjusting waveguide loss Insulator 123 electrodes of the thin film resistor 122 microwave bypass capacitor elements constituting the electrode 120A coplanar microwave delay line 121 impedance matching thin film resistance elements of the electrode 117 output optical amplifiers of the amplifier

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H04B 10/18 (72) Inventor Yuzo Yoshikuni 1-6, Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph Phone Co., Ltd.

Claims (2)

[Claims] 1. An optical short pulse generating light source, an optical branching circuit for branching the output light from this light source into N optical waveguides, and an optical branching circuit which is derived from this optical branching circuit and is output from said optical short pulse generating light source. N optical waveguide delay lines having different lengths provided so as to have a delay time difference corresponding to 1 / N of the optical pulse period, and N absorption-type lights interposed on the N optical waveguide delay lines A semiconductor optical signal output device in which a modulator, N optical amplifiers, and an optical merging circuit that collectively outputs the N optical waveguide delay lines are output on a semiconductor substrate. 2. The semiconductor optical signal output device according to claim 1, wherein the semiconductor substrate is semi-insulating, and is formed on the semiconductor substrate as a power supply circuit for supplying electric signals to N absorption type optical modulators. An absorption type optical system having N microwave delay lines, and the delay time of the electric signal in the N microwave delay lines is connected to the microwave delay lines from the time when the driving signal of the optical short pulse generating light source is input. A semiconductor optical signal output device, wherein the delay time before reaching the modulator is the same.