JPH05150202A - Optical transmission device for parallel transmission - Google Patents

Abstract

PURPOSE:To obtain the optical transmission device for parallel transmission of simple constitution which eliminates the need for an array of light emitting elements by providing a light source, a hologram for branching, a light intensity modulator, and a fiber array. CONSTITUTION:The light projected from a laser diode 1 is split by the multi- branching hologram 3 by the number (n) of channels and the respective (n) branch light beams are made parallel by a collimator lens 4 and made incident on an ultrasonic light wave intensity modulator 5. The light which is made incident on the ultrasonic wave light intensity modulator 5 is modulated corresponding to respective channel signals from a modulator driver 6 and sent by the fiber array 8. Thus, the parallel signals are sent as they are without being multiplexed to omit a circuit for parallel-serial conversion, etc. Further, the transmission speed may be equal to that of the respective channel signals, so neither an optical element nor an electric circuit need not have high speediness and relatively inexpensive ones are usable, so the cost is reducible. Further, no array light source is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter for optical fiber transmission, and more particularly to an optical transmitter for parallel transmission used in an optical transmitter for parallel transmission.

[0002]

2. Description of the Related Art In order to increase the transmission distance, improve the resistance to electromagnetic noise, and increase the speed, data is transmitted through optical fibers between computer terminals or between devices. As this system, there are used a system in which signals of a large number of channels are multiplexed and transmitted by one fiber, and a system in which light emitting elements and light receiving elements corresponding to the number of channels are arrayed and transmitted by a fiber array.

In the former method, time division multiplexing is mainly used. The basic configuration of this system is shown in FIG. As shown in this figure, in this configuration, first, the electrical signals of a plurality of channels are converted into serial signals by the parallel-serial conversion circuit 11 and multiplexed. Next, the multiplexed electric signal is passed through the light emitting element driver 12, converted into an optical signal by the light emitting element 13, and transmitted. Since this optical signal is time-division multiplexed as a whole, it becomes faster than the transmission rate of each channel.

The optical signal passing through the integrated optical fiber 14 is received by the light receiving element 15, converted into an electric signal by the light receiving circuit 16, and then converted into a parallel signal by the serial-parallel conversion circuit 17. And divided into multiple channels.

The basic configuration of the latter method is shown in FIG. As shown in this figure, in this configuration, first, electric signals of a plurality of channels are respectively passed through the light emitting element driver 21, converted into optical signals by the light emitting element array 22, and transmitted by the optical fiber array 23 for the number of channels. To do.

The optical signal that has passed through the optical fiber array 23 is received by the light receiving element 24, passes through each light receiving circuit 25, is converted into an electrical signal, and is output to each channel.

[0007]

However, the former method requires the parallel-serial conversion circuit 11. That is, a circuit for converting a multi-channel signal into a time-division serial signal is required on the transmission side, and a circuit for converting a time-division serial signal into a multi-channel signal is required on the reception side. In addition, high speed is required for both the optical element and the electric circuit. That is, because the transmission speed becomes high,
A light-emitting element and a light-receiving element which respond at high speed and a high-speed electric circuit are required. Therefore, there is a problem that the entire configuration becomes complicated and the cost becomes high.

In the latter method, the parallel-
Although there is an advantage that an electric circuit such as the serial conversion circuit 11 is not necessary and the speed of the optical element and the electric circuit may be about the same as the transmission speed of each channel, the light emitting element array 22 can be manufactured with high yield. This is difficult, and this is an obstacle to realizing parallel transmission.

As an optical transmitter for parallel transmission which does not use the light emitting element array 22, there is known an optical transmitter for parallel interface as disclosed in Japanese Patent Laid-Open No. 64-23222.

The present invention has been made in consideration of such a situation. Without using the light emitting element array 22, light from a single light source is branched by a branching hologram and each branched light is converted into a light beam. The present invention provides an optical transmitter for parallel transmission in which optical signals are respectively modulated by an intensity modulator and optical parallel transmission is performed.

[0011]

SUMMARY OF THE INVENTION The present invention is directed to a light source for irradiating light for data transmission, a branching hologram for branching the light emitted from the light source into a plurality of lights, and each branched light beam. An optical transmitter for parallel transmission, comprising: a light intensity modulator that modulates a signal and transmits the signal to a fiber array. The light intensity modulator is preferably an ultrasonic light intensity modulator.

[0012]

According to the present invention, the light emitted from the light source is
The branched hologram is branched into a plurality of light beams, and the branched light beams are modulated into optical signals by the optical intensity modulator according to the transmission signals of the respective channels and transmitted by the fiber array.

With this configuration, since parallel signals are transmitted in parallel, extra circuits such as a parallel-serial conversion circuit can be omitted. Moreover, since the transmission speed may be the same as the signal speed of each channel, a relatively low speed is sufficient for both the optical element and the electric circuit, and a cost reduction effect can be expected. Furthermore, since a single light source is not used and no array light source is used, the yield in manufacturing the device is greatly improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. The present invention is not limited to this.

FIG. 1 is a structural explanatory view showing an embodiment of the present invention. In this figure, 1 is a laser diode, and the laser diode 1 is connected to a laser driver 2. An ultrasonic light intensity modulator 5 is arranged in the light emitting direction of the laser diode 1 via a multi-branching hologram 3 and a collimating lens 4.

The ultrasonic light intensity modulator 5 is electrically connected to the modulator driver 6. After the ultrasonic light intensity modulator 5, a condenser lens 7 for condensing on the fiber and a fiber array 8 are arranged.

The laser driver 2 is provided with an auto power control circuit (not shown) so that the optical output of the laser diode 1 does not fluctuate due to temperature fluctuations and the like, and the laser driver 2 uses this auto power control circuit. A constant direct current is supplied to the laser diode 1 so that a constant light output can be obtained from the laser diode 1.

The light emitted from the laser diode 1 is divided by the multi-branching hologram 3 into the number of channels n (n is an arbitrary natural number). The multi-branch hologram 3 has a surface of n
Each surface is provided with a grating, and each surface is configured to collect light at different points. The n branched lights are collimated by the collimating lens 4,
It is incident on the ultrasonic light intensity modulator 5.

The structure of the ultrasonic light intensity modulator 5 is shown in FIG. As shown in the figure, the ultrasonic light intensity modulator 5 changes the refractive index by propagating an elastic wave in a medium, and uses a material such as lithium niobate for the electrode 5a,
5b is provided to excite an elastic wave of a certain frequency.

When the light H enters substantially orthogonally to the elastic wave,
The periodic refractive index causes a diffractive effect. Bragg diffraction occurs when the incident angle and the frequency of the elastic wave are adjusted, and the emitted light is only the first-order diffracted light and the transmitted light. If the elastic wave intensity is changed so as to satisfy the condition, the ratio of the first-order diffracted light and the transmitted light changes. Therefore, a modulator can be obtained by using both first-order diffracted light and transmitted light.
In order to obtain a large / N, it is better to adopt the first-order diffracted light.

In this way, the light incident on the ultrasonic light intensity modulator 5 is modulated according to each channel signal from the modulator driver 6. The light intensity-modulated light is condensed by the condenser lens 7, taken into the fiber array 8, and transmitted. When the core diameter of the fibers of the fiber array 8 is large, the condenser lens 7 can be omitted.

The operation in such a configuration will be described below. The light emitted from the laser diode 1 is divided by the multi-branching hologram 3 into the number of channels n, and the respective branched lights divided into n are collimated by the collimating lens 4 to generate an ultrasonic light intensity modulator. It is incident on 5. The light incident on the ultrasonic light intensity modulator 5 is modulated according to each channel signal from the modulator driver 6, and the modulated light is condensed by the condenser lens 6 and transmitted by the fiber array 8. To be done.

In this way, parallel signals can be transmitted as they are without being multiplexed, so that a circuit such as parallel-serial conversion can be omitted. Further, since the transmission speed may be the same as that of each channel signal, neither high speed is required for the optical element and the electric circuit, and a relatively inexpensive one can be used, and cost reduction can be expected. Further, since only one light emitting element driven by direct current is required without using the array light source, the yield is greatly improved.

[0024]

According to the present invention, the light from the light source is branched by the branching hologram, and each branched light is modulated into an optical signal by the light intensity modulator and transmitted to the fiber array. An optical transmitter for parallel transmission that is simple and does not need to use an array of light emitting elements can be realized.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a structural explanatory view showing a structure of an ultrasonic light intensity modulator.

FIG. 3 is an explanatory diagram showing a conventional time division multiplexing optical fiber transmission system.

FIG. 4 is an explanatory diagram showing an optical fiber transmission system using a conventional light emitting element array.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode 2 Laser driver 3 Hologram for multi-branching 4 Collimation lens 5 Ultrasonic light intensity modulator 6 Modulator driver 7 Focusing lens 8 Fiber array

Claims (2)

[Claims] 1. A light source for irradiating light for data transmission, a branching hologram for branching the light radiated from the light source into a plurality of lights, and an optical signal for modulating each branched branch light into a fiber array. An optical transmitter for parallel transmission, comprising: a light intensity modulator for transmitting. 2. The optical transmitter for parallel transmission according to claim 1, wherein the light intensity modulator is an ultrasonic light intensity modulator.