JPS60126935A - Optical time-division multiplex transmitter - Google Patents

Abstract

PURPOSE:To obtain high-speed time-division multiplex light pulses of several GHz which can not be obtained by the direct modulation of a conventional light emitting element by using a high-speed optical multiplexer as an optical time- division multiplexing device as to a device which is used for optical fiber communication and measurement. CONSTITUTION:The optical multiplexer 6 uses a PLZT thin film grown on a sapphire substrate as a waveguide material to form 2X1 internal total reflection (TIR) optical switches. A semiconductor laser with a 1.3mum band is used as a light emitting element 4 and coupled directly with the optical multiplexer 6 through a polarization plane conservative optical fiber. A clock signal generating circuit 13 generates a basic clock 7 of 3.2GHz to put the optical multiplexer 6 at 3.2GHz. Further, the basis clock signal 7 is frequency-divided by two to generate a reciprocal clock signal 12 of 1.6GHz, which is delayed by a clock signal delay circuit 11 and then applied to a driving circuit 2 to generate a light pulse driving signal corresponding to the input signal, thereby generating light pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical time division multiplex transmission device used for optical fiber communication and measurement.

Structure and Seven Problems of the Conventional Example FIG. 1 shows the conventional example. Conventionally, in optical time division multiplexing transmission, a plurality of electrical input signals 1 are synchronized with a clock signal 28 from a clock signal generation circuit 30 and a latch circuit 22 is used.
After sampling, the electrical multiplexer 24 switches in synchronization with the clock 29 to perform time division multiplexing.

Thereafter, the light emitting element 27 driven by the drive circuit 26 performs electrical-to-optical conversion and sends the optical time-division multiplexed light to the optical fiber 10. - The destination fiber has a single mode optical fiber with a bandwidth of 3 dB over 30 Gl-IZ JXn in the wavelength range of Q08 to 1.7 μm, and has a bandwidth of ij 3 THz n or more at both dispersion points. . For example, in a 10oKm single mode optical fiber, [Q, 3(,H
, it has a transmission bandwidth of 1d900G14 or more at the zero dispersion point wavelength. On the other hand, conventional direct modulation of semiconductor lasers has only been able to obtain a modulation band of at most 1 to 2 G + -1z, and the large transmission band of optical fibers has not been effectively utilized.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an optical time division multiplexing transmission device with excellent high-speed response.

Structure of the Invention The present invention has a plurality of electrical inputs and a clock generation circuit, a delay circuit that delays a clock from the clock generation circuit, and a delay circuit that delays a clock from the clock generation circuit, and a delay circuit that delays a clock from the electrical signal input from the electrical signal input in synchronization with the clock delayed by the delay circuit. multiple light-emitting element drive circuits that convert electrical signals into pulse signals and drive light-emitting elements;
a light-emitting element that converts the pulse signal into an optical pulse signal; an optical fiber that guides the optical pulse from the optical fiber; an optical multiplexer that outputs any one of the pulses, an output section that takes out the output light of the optical multiplexer, and an optical multiplexer drive circuit that generates the control signal that drives the optical multiplexer using a clock signal from the clock generation circuit. It consists of an optical time division multiplex transmission device with metal fittings.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows an embodiment of the present invention. The optical time division multiplex transmission device 201+'j is a module consisting of nine parts described below. The figure shows a case where the number of signal inputs is two. A drive circuit 2 that converts two electric power sources 1 into electric pulse signals 14 in synchronization with a clock signal 3, a light emitting element 4 that converts the electric pulse signals 14 into optical pulse signals, and an optical fiber that guides the respective optical pulse signals. 6. An optical multiplexer 6 that switches and multiplexes the optical pulse signals in the two optical fibers 5 at a predetermined timing, an output section that takes out the output light from the optical multiplexer 6, and an electrode 9 of the optical multiplexer with a clock signal. an optical multiplexer drive circuit 8 that drives at a predetermined timing in synchronization with 7; a clock signal generation circuit 13 that generates clock signals 7 and 12i;
The clock signal delay circuit 11 delays the clock signal 12 to a predetermined timing.

The optical multiplexer 6 is made of P grown on a sapphire substrate.
LZT thread thin film gold thin film is used as path material, total internal reflection (T
An IR) type 2×1 optical switch was fabricated. Waveguide width 20μm, waveguide crossing angle 2°, driving voltage approximately 10V
1. Extinction ratio was 15dB. The response speed of the switch is 4
It was higher than the G ratio.

A 1.3 μm band semiconductor laser is used as the light emitting element 4, and is directly coupled to the optical multiplexer 6 via a polarization maintaining optical fiber. The coupling loss was approximately 7 dB.

Since the PL, Z'l' thread TIR type optical multiplexer 6 has a polarization dependence on the driving voltage, the polarization direction of the light emitted from the optical fiber is changed at the coupling part between the optical fiber 6 and the optical multiplexer 6. The optical multiplexer 6 is coupled in the direction of the low driving voltage. The output light from the optical multiplexer 6 is directly coupled to the optical fiber 1o at the output section.

The clock signal generation circuit 13 generates a 3.2 GHz basic clock 7, and the optical multiplexer 6 is connected to the 3.2 GHz basic clock 7.
I got it working with Ilz. Also, basic clock signal 7ff:2
Divide the frequency to create a reciprocal clock signal 12 of 1.8Gl7,
After being delayed by the clock signal delay circuit 11, in addition to the drive circuit 2, an optical pulse driving signal corresponding to the input signal was generated to generate an optical pulse. At the coupling portion between the optical fiber 6 and the optical multiplexer 6, the delay time of the clock delay circuit was adjusted so that each optical pulse would arrive at a predetermined timing. The principle of multiplexing will be explained using the timing chart shown in FIG. In the figure, (g) indicates the voltage applied to the optical multiplexer at the basic frequency clock (period T=312.5 picoseconds). When a voltage is applied, an optical pulse of CH/L/1 is output to the optical multiplexer, and when the voltage is zero, an optical pulse of CH/L/2 is output.

FIGS. 3(d) and 3(e) show clock signals supplied to the clock signal delay circuit 11 corresponding to two inputs, respectively. FIG. 3(a) shows the optical pulse signal output of Chan*/L/1 at the LD optical multiplexer input section, and (
b) Kechiyatsuki/L'2 is shown. FIG. 2C shows the waveform of the multiplexed output light at the output section of the optical multiplexer. As shown in the figure, the fundamental frequency is 6.4GI-1z
It was possible to obtain a time-division multiplexed optical pulse of a signal with a chit/L'1.2. Approximately 0.0% in light output. emW peak values were obtained.

In this way, according to the present invention, an optical time division multiplex transmission device with excellent high-speed response has been realized.

In addition, in this embodiment, the number of inputs (multiplexing) is 2VC,
The number of poles of the optical multiplexer need only be (number of inputs)×1.

Further, the basic switch element in the optical multiplexer is not limited to a TIR type optical switch, and any two-manufactured one (straddle) output optical switch such as a directional coupler type optical switch may be used. In addition, in the waveguide,
The PLZT yarn thin film grown on the sapphire substrate is not limited to this, for example, Ti-diffused LiNb
Any waveguide material may be used as long as it has an electro-optic effect in the switch portion, such as a 0 s waveguide, an ion exchange LiNb0 s waveguide, or a liquid crystal waveguide. In addition, although a semiconductor laser was used as a light emitting element, a light emitting diode or S
LD may also be used. Although direct coupling was used to couple the light emitting element and the optical fiber, any type of coupling, such as lens coupling, tapered fiber coupling, or tapered tip coupling, may be used as long as the function is not impaired. In addition, direct coupling was used to couple the optical fibers in the input/output section with the optical multiplexer, but it is also possible to couple the optical fibers by lens coupling, lens and prism coupling, lens and grating coupling, etc. However, there is no problem.

Alternatively, the output light of the optical multiplexer may be output directly to the end of the optical connector using a lens or a grating.

Effects of the Invention In the present invention, by using a high-speed optical multiplexer as an optical time-division multiplexing device, it has become possible to obtain high-speed time-division multiplexed optical pulses of several GHz, which could not be obtained by conventional direct modulation of light emitting elements. .

According to the present invention, it is possible to provide an optical time division multiplex transmission device having the above effects.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional optical time division multiplexing transmission device, FIG. 2 is a schematic diagram of the same device according to an embodiment of the present invention, and FIG.
) to (0 is a time chart showing the operation of the embodiment. 1...Input electrical signal, 2...Light emitting element drive circuit, 3.7.12... clock signal, 4
...... Light emitting element, 6.10... Optical fiber, 6, ... Optical multiplexer, 8...
・Optical-7・multiplexer drive circuit, 9... optical multiplexer drive electrode, 11...°° clock timing adjustment circuit, 13... clock generation circuit,
14...Light emitting element drive electric signal pulse, 2o.
...Optical time division multiplex transmission equipment. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 η Figure 3

Claims (1)

[Claims] Has multiple electrical signal inputs and clock generation circuits,
a delay circuit that delays a clock from the clock generation circuit; a plurality of light emitting element drive circuits that convert an electrical signal from the electrical signal input into a pulse signal to drive the light emitting elements in synchronization with the clock delayed by the delay circuit; , a light emitting element that converts the pulse signal into a light pulse signal, an optical fiber that guides the light pulse from the light emitting element, and a light emitting element that guides a plurality of light pulses from the optical fiber and that is switched by a control signal to produce a plurality of light pulses. an optical multiplexer that outputs any one of the optical pulses, an output section that takes out the output light of the optical multiplexer, and an optical multiplexer drive that generates all of the control signals that drive the optical multiplexer with a clock signal from the clock generation circuit. An optical time division multiplex transmission device comprising a circuit.