JPH03270520A - Optical repeater - Google Patents

Abstract

PURPOSE:To repeat a supervisory signal in the optical direct amplification system by using an erbium doped optical fiber or a high dispersion optical fiber and applying AGC amplification to a signal branched optically, amplitude- modulating the resulting signal with a monitor system signal to apply optical direct amplification and relating the amplified signal. CONSTITUTION:The gain of a laser diode 15 in a preamplifier section is controlled by a supervisory section 10, induced stimulation is caused from an optical coupler 11, from which a pump light for optical direct amplification is generated. A photoelectric converter 16 converts an optical signal branched by a beam splitter 12 into an electric signal, from which a desired supervisory system, signal is extracted. Then only a signal at a desired frequency band passes through a filter 18 and is given to the monitor section 10. The supervisory signal from the section 10 is converted by a laser diode 17 at a post-stage amplifier section into an optical signal, which is used to apply amplitude modulation to an optical output from an AGC amplifier 13 and the result is subject to optical direct amplification and the result is sent to an optical fiber 1.

Description

[Detailed Description of the Invention] [Summary] Regarding the method of directly amplifying and relaying optical signals, we have realized a method in which the light itself is the target of relay processing using an Er-doped optical fiber amplification method or an optical fiber Raman amplification method. With the purpose of
The C-amplified signal is amplitude-modulated by a monitoring system signal, optically directly amplified, and then relayed.

[Industrial application field]

The present invention relates to an optical repeater, and more particularly to a method for directly amplifying and repeating optical signals.

Optical repeaters currently in practical use use a method in which light is first converted into electricity in the repeater, amplified and shaped, and then this electrical signal is returned to light using a semiconductor laser, etc. Then, (1) the speed of the signal to be processed is limited by the bit rate determined by the electrical circuit, and (2) the optical wavelength that can be used is limited.

On the other hand, optical repeaters that directly amplify and shape optical signals and relay them can: ■ Change the bit rate at any time up to around 10 Gb/s; ■ Bidirectional amplification and batch amplification of wavelength multiplexed signals are also possible. Therefore, from these points, there is a demand for the adoption of an optical direct relay system.

[Conventional technology and its issues]

Direct optical amplification methods currently being researched include amplification methods using Er (erbium)-doped optical fibers, semiconductor lasers, optical fiber Ramans, etc.; noise is generated,
(2) It is preferable to use an Er-doped optical fiber or an optical fiber Raman amplification method in view of product variations.

However, at present, no optical repeater has been proposed that uses an Er-doped optical fiber amplification method or an optical fiber Raman amplification method to relay (drop insert) a monitoring system signal.

Therefore, it is an object of the present invention to realize a system in which light itself is subject to relay processing using an Er-doped optical fiber amplification system or an optical fiber Raman amplification system.

[Means to solve the problem]

In order to solve the above problems, in the optical repeater according to the first aspect of the present invention, as conceptually shown in FIG. an optical coupler 2 for splitting the optical output from the optical coupler 2, a beam splitter 3 for splitting the optical output from the optical coupler 2, an optical-to-electrical converter 4 for converting the branched light from the beam splitter 3 into an electrical signal, AG that amplifies the signal with a fixed time constant
C amplifier 5, a filter 6 for extracting a monitoring system signal from the electrical signal, a monitoring section 7 for dropping the monitoring system signal and inserting another monitoring system signal, and an output signal of the monitoring section 7. an electric-to-optical converter 8 that converts the amplitude-modulated output signal of the AGC amplifier 5 into the pump light, and is configured such that the time constant is large enough to be unaffected by the period of the monitoring signal. are doing.

The second optical repeater according to the present invention, as conceptually shown in FIG. a first optical coupler 11 and a first optical coupler 11 that branches a monitoring system signal from the optical output of the first optical coupler 11 and supplies it to the monitoring unit 10;
a beam splitter 12, a second optical coupler 2 for directly amplifying the light by giving pump light to the optical input from the first beam splitter 12, and the second optical coupler 2.
a second beam splitter 3 for splitting the optical output from the
An optical-to-electrical converter 4 that converts the branched light from the second beam splitter 3 into an electrical signal, an AGC amplifier 5 that amplifies the electrical signal with a constant time constant, and an output signal of the AGC amplifier 5 that converts the split light from the second beam splitter 3 into an electrical signal. an optical AGC amplification unit 13 configured with an electric-to-optical conversion unit 8 that converts into pump light to the second optical coupler 2;
The third optical coupler 14 post-amplifies the output of the optical AGC amplification section 13 using pump light from the monitoring section 10.

Furthermore, in the optical repeater according to the third aspect of the present invention, as conceptually shown in FIG. 15, both optical AGC amplification sections 13.15 perform optical AGC amplification on one of the optical inputs, the beam splitter 12 performs branching on the optical inputs in both directions, and The three optical couplers 11 and 14 are configured to perform optical amplification in opposing directions.

In any of the present inventions, a high dispersion optical fiber that performs optical fiber Raman amplification may be used instead of the erbium-doped optical fiber.

[For production]

In the first invention shown in FIG.
Bumping is performed using pump light from
) 4 to convert to electrical output.

The AGC amplifier 5 performs automatic gain control so that its electrical output is constant, and outputs it to the electrical-optical converter 8.

On the other hand, from the electrical output from the optical-to-electrical converter 4, only a monitoring signal is extracted by a filter 6 and sent to a monitoring section (SV) 7, where it is dropped as appropriate and, for example, a monitoring signal from the opposite line is inserted. and sends it to the electrical-optical converter 8.

At this time, the input to the electric-optical converter 8 is the AGC amplifier 5.
The output of and the output of the monitoring section 7 are combined, but
The output of the AGC amplifier 5 exhibits a constant level as shown in the characteristic curve A in FIG. 4, and since the time constant is large, the monitoring system signal from the monitoring section 7 is amplitude-modulated from this curve A, as shown in the curve B. Become.

The electrical-optical converter 8 converts the human-powered electrical signal into light and supplies it to the optical coupler 2 as pump light.

In this way, the repeater monitoring system signal can be handled using the optical direct amplification method.

However, in the first invention shown in FIG.
Since the amplitude of the optical signal is averaged by the AGC operation,
There are disadvantages in that the degree of modulation decreases (the supervisory signal becomes weaker), the demodulation performance of the supervisory signal deteriorates, and the supervisory signal from the opposite line is picked up.

Therefore, in the second invention shown in FIG. 2, in order to branch the monitoring system signal before performing AGC amplification, the optical fiber 1
The monitoring system signal passing through the first beam splitter 12
After branching at
and an electric-to-optical converter 8), and a third optical coupler 13 on the output side of the repeater performs AGC amplification.
The above-mentioned drawbacks are solved by amplitude modulating (and optical direct amplification) the monitoring system signal from.

However, since the optical input signal to the repeater is attenuated, the optical AGC amplifier 5 does not perform the AGC operation before separating the monitoring system signal, and the pump light from the monitoring unit 10 causes the first optical coupler 11 to Perform preamplification with .

Therefore, the repeater has a three-stage amplification structure consisting of optical couplers 11, 2, and 14. Of these, the optical amplification by optical couplers 11 and 14 is directly related to the monitoring system signal, but the optical AGC amplification section 13 is completely separated from the monitoring system signal, and the amplitude modulation frequency of the monitoring system signal has no relation to the AGC time constant, so that the amplitude modulation is not affected by the AGC operation.

In the second invention described above, the optical input is limited to the left side in FIG. 2, but in the third invention shown in FIG.
An optical AGC amplification section 15 having the same configuration as the C amplification section 13 is provided in the opposite amplification direction with the beam splitter 12 in between, and the beam splitter 12 can split optical input in both directions, and the optical couplers 11 and 14 can Since optical amplification is performed in directions facing each other, optical input in either direction is optically amplified by the optical coupler 11 or 14, AGC amplified by the optical AGC amplification section 15 or 13, and then output from the beam splitter 12. A monitoring system signal can be branched to the monitoring section 10, and the same operation as shown in FIG. 2 can be realized.

In this case, one of the optical couplers and the optical AGC amplification section will pass the optical input as is.

(Embodiment) FIG. 5 shows an embodiment of an optical repeater according to the second invention. In this embodiment, an erbium-doped optical fiber (or high dispersion optical fiber) 1 and an optical coupler are connected. 11 and a laser diode (LD) 15 constitute a preamplification section, and the gain of the laser diode 15 is controlled by the monitoring section 10 to cause stimulated emission from the optical coupler 11 to generate pump light for direct amplification of light. It's starting to happen.

In addition, the beam splitter 12, the optical-to-electrical converter 16, and the bandpass filter 18 constitute a monitoring system signal extraction section, and the optical signal split by the beam splitter 12 is converted into an electric signal by the optical-to-electrical converter 16. In order to convert the signal into a signal and extract a desired monitoring system signal from this signal, only that frequency band is passed through the filter 18 and provided to the monitoring section 10.

Further, after the optical AGC amplification section 13, a post-amplification section composed of an optical coupler 14 and a laser diode 17 is provided, and the monitoring signal from the monitoring section 10 is converted into an optical signal by the laser diode 17, and the optical With coupler 14, optical AC,
The optical output from the C amplifier 13 is amplitude-modulated, directly amplified, and sent to the optical fiber l.

As shown in the figure, such optical repeaters are similarly provided for opposite lines, and monitoring system signals are exchanged between the monitoring sections of each optical repeater. In addition, POW was provided separately from the optical fiber! A power supply device is shown in which power is supplied from the terminal station via line 2 (12) and is supplied to both optical repeaters.

FIG. 6 shows an embodiment of the third invention, in which the optical amplification direction of the optical coupler 14 is reversed compared to the embodiment of FIG. 5, and the optical AGC An optical AGC amplification section 15 provided opposite to the amplification section 13 is arranged symmetrically with the beam splitter 12 in between.

Further, the downstream optical output branched by the beam splitter 12 is converted into an electrical output by the optical-to-electrical converter 21, and the received optical power level is monitored by the monitoring unit 10, and the monitoring system signal ( The frequency fsv) is taken out and given to the monitoring section 10. On the other hand, the upstream optical output is -
The electrical converter 22 converts it into an electrical output and monitors the optical power level, and the bandpass filter 24 takes out the upstream signal monitoring system signal (frequency fsV·), which is then monitored by the monitoring unit 10.

By doing so, it is possible to perform relay operations for both upstream optical signals and downstream optical signals using one optical repeater.

〔Effect of the invention〕

As described above, according to the optical repeater of the present invention, the optically branched signal is AGC-amplified using an erbium-doped optical fiber or a high-dispersion optical fiber, and the AGC-amplified signal is amplitude-modulated by a monitoring system signal. Since the system is configured to directly amplify and relay optical signals, monitoring system signals can be relayed using the optical direct amplification method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of an optical repeater according to the first invention, FIG. 2 is a diagram showing the basic configuration of an optical repeater according to the second invention, and FIG. 3 is a diagram showing the basic configuration of an optical repeater according to the second invention. , FIG. 4 is a waveform diagram for explaining optical amplitude modulation by the optical repeater according to the present invention, and FIG. 5 is a diagram showing the basic configuration of the optical repeater according to the third invention. FIG. 6 is a circuit block diagram showing an embodiment of the third invention. FIG. 6 is a circuit block diagram showing an embodiment of the third invention. In FIG. 1, 1... Erbium-doped (high dispersion) optical fiber, 2.
11.14... Optical coupler, 3.12... Beam splitter, 4... Optical-electrical converter, 5... AGC amplifier, 6... Band pass filter, 7.10... Monitoring section, 8... Electricity-optical conversion section. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] (1) Optical coupler (for direct amplification of light by applying pump light to the optical input of the erbium-doped optical fiber (1)
2), a beam splitter (3) that splits the optical output from the optical coupler (2), and an optical-to-electrical converter (4) that converts the split light from the beam splitter (3) into an electrical signal. and an AGC amplifier (5) that amplifies the electrical signal with a constant time constant.
), a filter (6) that extracts a monitoring signal from the electrical signal, a monitoring section (7) that drops the monitoring signal and inserts another monitoring signal, and an output of the monitoring section (7). an electro-optical converter (8) that converts the output signal of the AGC amplifier (5), which is synthesized with the signal and amplitude-modulated, into the pump light, and the time constant is not affected by the period of the monitoring signal. An optical repeater characterized by being relatively large. (2) a first optical coupler (11) that pre-amplifies the optical input of the erbium-doped optical fiber (1) with pump light controlled by the monitoring unit (10); a first beam splitter (12) that branches a monitoring system signal from the optical output and provides it to the monitoring section (10); and a pump light that provides pump light to the optical input from the first beam splitter (12). a second optical coupler (2) for directly amplifying light; a second beam splitter (3) for splitting the optical output from the second optical coupler (2); An optical-to-electrical converter (4) that converts the branched light from the splitter (3) into an electrical signal, an AGC amplifier (5) that amplifies the electrical signal with a constant time constant, and an output of the AGC amplifier (5). and an electric-optical converter (8) that converts the signal into pump light for the second optical coupler (2).
a GC amplification section (13); and a third optical coupler (14) that post-amplifies the output of the optical AGC amplification section (13) using pump light from the monitoring section (10).
), and an optical carrier. (3) Another optical AGC amplifier (15) having the same configuration as the optical AGC amplifier (13) is provided in the reverse amplification direction across the first beam splitter (12), and both optical AGC amplifiers ( 1
3) (15) performs optical AGC amplification for one optical input, the beam splitter (12) performs branching for optical input in both directions, and furthermore, the first and third optical couplers ( 11) The optical carrier according to claim 2, wherein the optical carriers (14) perform optical amplification in opposite directions. (4) The optical repeater according to any one of claims 1 to 3, characterized in that a high dispersion optical fiber that performs optical fiber Raman amplification is used in place of the erbium-doped optical fiber (1).