JPH06125308A - Optical signal transmitter - Google Patents

Abstract

PURPOSE:To obtain the optical signal transmitter not requiring lots of elements for monitoring an optical output in which a laser elements array and a drive element array are arranged close to each other. CONSTITUTION:The transmitter is provided with a laser element array 20 comprising plural laser elements and with a drive element array 14 comprising plural drive elements driving the laser elements, and plural optical fibers 24a-24f are coupled optically with each laser element. An optical signal outputted from a laser element 20f in the laser element array 20 sending a clock signal is branched by a branch means 26 and the branched monitor optical signal is received by a light receiving element 28 and a drive current of each drive element of the drive element array 14 is controlled based on the intensity of the received monitor optical signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmitter in an optical transmission system for transmitting an optical signal using a plurality of optical fibers.

[0002]

2. Description of the Related Art In an optical transmission system for transmitting an optical signal by using a plurality of optical fibers, an electric signal is converted into an optical signal by a laser element on a transmitting side and transmitted to an optical fiber,
An optical signal sent by an optical fiber on the receiving side is converted into an electric signal by a light receiving element.

When a laser element is used as a light emitting element on the transmitting side, the threshold value and the optical output of the laser element have temperature dependence, so the drive current of the laser element is controlled so that the output of the laser element becomes constant. There is a need. A conventional optical transmission system is shown in FIG. In the optical transmission system, the optical signal transmission device 2 on the transmission side and the optical signal reception device 4 on the reception side are connected by an optical transmission line 6.

The optical signal transmitter 2 is provided with a signal source 10 for outputting an electric signal to be transmitted and a clock transmission source 16 for outputting a clock signal, and a signal line 12 is provided to the signal source 10 and the clock transmission source 16. A drive element array 14 for driving the laser is connected via the. Drive element array 1
A laser element array 20 is connected to 4 via a signal line 18. The laser light from the laser element array 20 is transmitted by the lens array 22 to the optical fiber 24a of the optical transmission line 6.
Optically coupled to ~ 24f.

The optical signal receiving device 4 is provided with a light receiving element array 38 for receiving the transmitted optical signal, and is optically coupled to the optical fibers 24a to 24f of the optical transmission line 6 by the lens array 36. The light receiving element array 38 has a signal line 40
The amplifier array 42 is connected via. The optical signal received by the light receiving element array 38 is transferred to the amplifier array 42.
Is amplified by and extracted as an electric signal.

In the conventional optical signal transmitter 2, in order to monitor the optical output of each laser element in the laser element array 20, as shown in FIG. 3, a light receiving element array 50 is provided on the rear end face side of the laser element array 20. The amplifier array 52 is provided, each monitor signal is input to the drive element array 14 via the signal line 54, and each drive current is controlled based on the optical output from the rear end face of each laser element.

[0007]

As described above, in the conventional optical signal transmitting apparatus, since the optical output of each laser element is monitored and the drive current is controlled, the accuracy suitable for each laser element of the laser element array 20 is obtained. However, there is a problem that a large number of light receiving elements and amplifiers are required.
Further, since the light receiving element array 50 and the amplifier array 52 need to be arranged close to the rear end face side of the laser element array 20, the laser element array 20 and the driving element array 14 must be arranged separately. There is a problem in that the signal lines between these arrays are crossed and the structure becomes complicated.

An object of the present invention is to provide an optical signal transmitting apparatus which does not require a large number of elements for monitoring the optical output and which can arrange the laser element array and the driving element array in close proximity. .

[0009]

The above object has a laser element array having a plurality of laser elements, and a drive element array having a plurality of drive elements for driving each laser element of the laser element array. In an optical signal transmission device in which a plurality of optical fibers are optically coupled to each laser element of a laser element array, among the plurality of laser elements of the laser element array, from an optical signal output from a laser element transmitting a clock signal, Based on the intensity of the monitor optical signal received by the light receiving element, the monitor has an optical signal for branching and a light receiving element for receiving the monitor optical signal branched by the branching means. An optical signal transmitting device is characterized by controlling the drive current of each drive element of the drive element array.

[0010]

According to the present invention, among the plurality of laser elements of the laser element array, the optical signal output from the laser element transmitting the clock signal is branched by the branching means, and the branched optical signal for monitoring is received by the light receiving element. The drive current of each drive element of the drive element array is controlled based on the intensity of the received monitoring optical signal, so that the output of the laser element array is accurately monitored by a small number of elements. Therefore, the laser element array and the driving element array can be arranged close to each other.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical transmission system according to an embodiment of the present invention will be described with reference to FIG. The same components as those of the conventional optical transmission system shown in FIG. 3 are designated by the same reference numerals to omit or simplify the description. Also in the optical transmission system of the present embodiment, the optical signal transmitting device 2 on the transmitting side and the optical signal receiving device 4 on the receiving side are connected by the optical transmission line 6.

The optical signal transmission device 2 is provided with a signal source 10 for outputting an electric signal to be transmitted and a clock transmission source 16 for outputting a clock signal, and a signal line 12 is provided to the signal source 10 and the clock transmission source 16. A drive element array 14 for driving the laser is connected via the. Drive element array 1
4 is provided adjacent to the laser element array 20, and these are connected by a short signal line 18. The laser light from the laser element array 20 is optically coupled to the optical fibers 24a to 24f of the optical transmission line 6 by the lens array 22.

The optical signal receiving device 4 is provided with a light receiving element array 38 for receiving the transmitted optical signal, and is optically coupled to the optical fibers 24a to 24f of the optical transmission line 6 by the lens array 36. The light receiving element array 38 has a signal line 40
The amplifier array 42 is connected via. The optical signal received by the light receiving element array 38 is transferred to the amplifier array 42.
Is amplified by and extracted as an electric signal.

In the optical signal transmitter 2 of this embodiment, in order to monitor the optical output of the laser element array 20, the laser element 20f which outputs a clock signal is selected from the laser elements in the laser element array 20, This laser element 20f
Monitor the optical output of. That is, the lens array 22 for condensing the optical signal of the laser element 20f and the optical fiber 24f
A half mirror 26 is provided between the two and to split the optical signal output from the laser element 20f to the optical fiber 24f. It is desirable that the intensity of the monitor optical signal branched by the half mirror 26 and output by the light receiving element 28 be 1/3 or less of the intensity of the optical signal input to the half mirror 26. This is to ensure the intensity of the optical signal of the clock signal output to the optical fiber 24f to be sufficient for receiving at the receiving side. Further, as the laser element 20f that outputs the clock signal, as shown in FIG.
It is desirable to arrange it at the end of the laser element array 20.
This is to prevent the signal lines from interlacing and complicating the structure.

The branched light is received by the light receiving element 28, which is a photodiode, and converted into an electric signal. The light receiving element 28 is connected to the amplifier 32 via the signal line 30. The amplifier 32 amplifies the converted electric signal.
The monitor signal amplified by the amplifier 32 is sent to the signal line 34.
Is input to each drive element of the drive element array 14 via.

Next, the operation of the optical transmission system according to this embodiment will be described. The electric signal output from the signal source 10 of the optical signal transmitter 2 is transmitted through the signal line 12 to the drive element array 1
Sent to 4. The drive element array 14 determines whether to bring each laser element of the laser element array 20 into a light emitting state or a light extinguishing state based on the sent electric signal. When the laser element emits light, it is driven by the corresponding drive element in the drive element array 14.

At this time, the light branched from the optical signal of the laser element 20f which outputs the clock signal is received by the light receiving element 28 and amplified by the amplifier 32, and each drive element of the drive element array 14 is amplified by the amplified monitor signal. To control the laser drive current. That is, the laser element 20f
If the intensity of the optical signal is lower than the predetermined value, the laser drive current by each drive element of the drive element array 14 is increased to increase the optical output of each laser element of the laser element array 20. On the contrary, when the intensity of the optical signal of the laser element 20f is higher than the predetermined value, the laser drive current by each drive element of the drive element array 14 is decreased and increased to increase the optical output of each laser element of the laser element array 20. To do.

The optical signal output from the laser element array 20 is output to the optical fiber arrays 24a to 24f of the optical transmission line 6 via the lens array 22 and transmitted to the optical signal receiving device 4 on the receiving side. Optical fiber arrays 24a-24f
The optical signal transmitted through the inside is received by the light receiving element array 38 via the lens array 22 which is optically coupled, and converted into an electric signal. The electric signal converted by the light receiving element array 38 is amplified by the amplifier array 42 via the signal line 40 and is taken out as a signal.

In this embodiment, since the optical output is monitored by the laser element 20f which outputs the clock signal from the laser element array 20, the optical signal can be accurately monitored and the influence on the entire optical transmission system is improved. Has the advantage of being less In the laser element that transmits the signal from the signal source 10, the driving state changes depending on the signal that is transmitted. On the other hand, since the clock signal is repeatedly turned on and off at regular intervals, the laser element 20f is turned on and off at regular intervals and the driving state is constant. Therefore, an accurate optical signal can be monitored by monitoring the optical output by the laser element 20f that outputs the clock signal. Further, it is known from the receiving side that the clock signal is always turned on and off at regular intervals. By branching the signal, the signal sent to the receiving side can be accurately received even if the strength thereof is low, and the influence on the entire optical transmission system can be reduced.

As described above, according to this embodiment, the output of the laser element array can be branched by the half mirror and accurately monitored by a small number of elements, and the laser element array and the driving element array are arranged in close proximity. be able to. An optical transmission system according to another embodiment of the present invention will be described with reference to FIG. The same components as those of the optical transmission system shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The optical transmission system of this embodiment differs from the optical transmission system shown in FIG. 1 in the optical signal branching means. That is, in the present embodiment, the fiber coupler 44 is provided as a branching unit in the portion of the optical fiber 24f that transmits the clock signal in the vicinity of the optical signal transmitter 2 to branch the optical signal. The optical signal input from the laser element 20f to the optical fiber 24f is branched in the optical fiber 24f. It is desirable that the intensity of the optical signal branched by the fiber coupler 44 and output by the light receiving element 28 be 1/2 or less of the intensity of the optical signal input to the fiber coupler 44. This is to ensure sufficient as the optical signal of the clock signal output from the optical fiber 24f to the receiving side.

The branched light is received by the light receiving element 28, which is a photodiode, and converted into an electric signal. The light receiving element 28 is connected to the amplifier 32 via the signal line 30. The amplifier 32 amplifies the converted electric signal.
The monitor signal amplified by the amplifier 32 is sent to the signal line 34.
Is input to each drive element of the drive element array 14 via.

As described above, according to this embodiment as well, the output of the laser element array can be branched by the fiber coupler and accurately monitored by a small number of elements, and the laser element array and the driving element array can be arranged close to each other. You can

[0024]

As described above, according to the present invention, among the plurality of laser elements of the laser element array, the optical signal output from the laser element transmitting the clock signal is branched by the branching means, and the branched optical signal is output. The signal is received by the light receiving element, and the drive current of each drive element of the drive element array is controlled based on the intensity of the received optical signal. It can be monitored and stable driving is possible. Further, the laser element array and the driving element array can be arranged close to each other, so that the signal lines do not intersect with each other and the structure is not complicated.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical transmission system according to another embodiment of the present invention.

FIG. 3 is a diagram showing a conventional optical transmission system.

[Explanation of symbols]

 2 ... Optical signal transmitter 4 ... Optical signal receiver 6 ... Optical transmission line 10 ... Signal source 12 ... Signal line 14 ... Driving element array 16 ... Clock source 18 ... Signal line 20 ... Laser element array 22 ... Lens array 24a ... 24f ... Optical fiber 26 ... Half mirror 28 ... Light receiving element 30 ... Signal line 32 ... Amplifier 34 ... Signal line 36 ... Lens array 38 ... Light receiving element array 40 ... Signal line 42 ... Amplifier array 44 ... Fiber coupler 50 ... Light receiving element array 52 … Amplifier array 54… Signal line

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01S 3/18 H04B 10/02

Claims (3)

[Claims] 1. A laser element array having a plurality of laser elements and a drive element array having a plurality of drive elements for driving each laser element of the laser element array, wherein each laser element of the laser element array is provided. In an optical signal transmission device in which a plurality of optical fibers are optically coupled, a branch for branching an optical signal for monitoring from an optical signal output from a laser element that transmits a clock signal among a plurality of laser elements of the laser element array. Means, and a light receiving element for receiving the monitor optical signal branched by the branching means, and each drive of the drive element array based on the intensity of the monitor optical signal received by the light receiving element. An optical signal transmitting device characterized by controlling a drive current of an element. 2. The optical signal transmitting apparatus according to claim 1, wherein the intensity of the monitor optical signal branched by the branching unit and output to the light receiving element is equal to the intensity of the optical signal input to the branching unit. An optical signal transmission device characterized by being 1/2 or less. 3. The optical signal transmitting apparatus according to claim 1, wherein a laser element for transmitting a clock signal is arranged at an end portion of the laser element array.