JP2669483B2 - Optical amplifier repeater circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an optical fiber communication system, and particularly to a long-distance optical fiber communication system including an optical submarine cable that crosses the ocean, and an optical amplification repeater for directly amplifying and repeating light. Circuit.

[0002]

2. Description of the Related Art Conventionally, a relay system of an optical fiber communication system temporarily converts an optical signal transmitted into an electric signal,
A so-called regenerative relay method has been adopted in which a signal is reproduced once, and then the reproduced electric signal is returned to an optical signal and transmitted to the next transmission section. On the other hand, the progress of optical direct amplification technology in recent years has increased the momentum of optical amplification relay in the field of optical relay transmission.

2 to 4 show a conventional optical amplifier circuit and an optical amplifier repeater circuit using the same.
2 and 3 are block diagrams showing the basic configuration of a conventional optical amplifier circuit, and FIG. 4 is a conventional optical amplifier repeater circuit using the optical amplifier circuit of FIG.

FIG. 2 shows the configuration of a basic circuit A for optical direct amplification. In the optical amplification circuit A, a fiber doped with a rare earth element (lanthanoid or actinoid) or a semiconductor laser amplifier is often used as an amplification medium. Here, an example is shown in which an erbium (Er) -doped fiber (hereinafter referred to as Er-doped fiber) 1 is used.

[0005] Reference numeral 2 denotes an excitation light source for exciting the Er-doped fiber 1, reference numeral 3 denotes a control circuit for controlling the excitation light source 2, and reference numeral 4 denotes a power supply circuit for supplying power to the control circuit 3. The pumping light source 2 is a high-power semiconductor laser, an InGaAsP / InP laser with an oscillation wavelength of about 1475 nm, or an oscillation wavelength of 98.
A 0 nm InGaAs / GaAs laser is often used.

After the output light La of the pumping light source 2 is converged on the optical fiber a, it is introduced into the Er-doped fiber 1 through the wavelength division ratio demultiplexer 5. Erbium doped in the Er-doped fiber 1 becomes excited by the output light La of the pumping light source 2 from the optical fiber a, and
It has an amplifying effect on the light of 570 nm.

In this example, the input signal light L1 having a wavelength of 1558 nm is transmitted by an optical fiber in the direction of the arrow and introduced into the Er-doped fiber 1. After being amplified in the Er-doped fiber 1, the input signal light L1 passes through the isolator 6 and the optical filter 7 via the wavelength division ratio demultiplexer 5, and becomes the amplified output signal light L1 '. The isolator 6 and the optical filter 7 may not exist.

FIG. 3 is a diagram showing an optical amplifying circuit B using a wavelength division ratio demultiplexing fiber coupler 8 instead of the wavelength division ratio division demultiplexer 5 of FIG. The wavelength division ratio demultiplexer 5 used in FIG. 2 and the wavelength division ratio demultiplexing fiber coupler 8 used in FIG. 3 have the same basic function, and light having different transmission characteristics with respect to light of different wavelengths. Parts. The wavelength division ratio demultiplexer 5 used in the optical amplification circuit A of FIG. 2 is basically a multilayer beam splitter, and outputs the output light La of the pumping light source 2.
Is reflected at 45 °, and the input signal light L1 passes straight through. The wavelength demultiplexing / demultiplexing fiber coupler 8 is an optical component realized by the fiber coupler.

FIG. 4 is a diagram showing a conventional optical amplification repeater circuit .alpha. Constructed by using a pair of the optical amplification basic circuits B and B'of FIG. The optical amplifier repeater α is transmitted in the second direction (hereinafter, referred to as “downward direction”) opposite to the first direction with the input signal light L1 transmitted in the first direction (hereinafter, referred to as “upward direction”). The input signal light L2 is output light La, L of the pumping light sources 2 and 2 '.
The output signal lights L1 'and L2' are amplified and relayed by a ', and optical components corresponding to the upstream direction are similarly arranged in the downstream direction.

That is, an Er-doped fiber 1 ', an excitation light source 2', a control circuit 3 ', an isolator 6', an optical filter 7 ', and a wavelength division ratio demultiplexing fiber coupler 8' are also arranged in the downstream direction. The power supply circuit 4 supplies electric power to the control circuits 3 and 3 ′ in both upper and lower directions, and a current I flows through the power supply line 9 to the power supply circuit 4. The optical amplification repeater circuit α as shown in FIG. 4 has a simpler structure than the regenerative repeater circuit.
Because it can easily cope with transmission speeds of the gigabit level without using high-speed electronic circuits, development is being advanced as a next-generation optical repeater circuit.

[0011]

However, the conventional optical amplifier repeater α shown in FIG. 4 has the following problems related to the reliability of the pumping light sources 2 and 2 '. That is, in the conventional optical amplification relay circuit α of FIG. 4, for example, when the pumping light source 2 fails, the Er-doped fiber 1 from which the output light La of the pumping light source 2 cannot be obtained is not pumped, and the optical signal L1 is absorbed in reverse. Therefore, the upstream signal is interrupted. That is, a system failure occurs.

In order to avoid this, the reliability of the pump light sources 2 and 2'must be significantly increased to the order of several fits. It is possible to make the pumping light sources 2 and 2 ′ redundant, but in addition to doubling the number of pumping light sources 2 and 2 ′,
Various additional functions such as a deterioration determination function and a redundancy switching function are required, and the merit of the optical amplification relay circuit α, which is characterized by a simple configuration, is diminished.

As described above, the conventional optical amplification relay circuit α originally has the advantages that the configuration is simple and the relay of the optical signals L1 and L2 on the order of gigabits can be easily achieved, but high reliability is required. There is a problem that it is extremely difficult to apply it to long-distance relay such as transoceanic. The present invention has been made in view of the drawbacks of the conventional optical amplification repeater circuit, and an object of the present invention is to provide an optical amplification repeater circuit applicable to a long-distance optical amplification repeater system.

[0014]

The above-mentioned conventional problems can be solved by the present invention by adopting the following novel characteristic constitution means. That is, a first feature of the present invention is an optical amplification repeater circuit of two-wire bidirectional optical communication for amplifying optical signals in a first direction and a second direction opposite to the first direction, respectively. First and second optical amplification fibers for amplifying signal light propagating in the first and second directions, respectively, first and second pump light sources, and the first and second pump light sources;
After combining the respective output lights of the pumping light source of
A single optical multiplexer / demultiplexer for demultiplexing into the first and second pumping lights respectively sent to the optical amplifying fiber, and a single common control circuit for integrally controlling the outputs of the two pumping light sources, A power supply circuit for supplying electric power to the control circuit is provided, and the two first and second pumping light sources are controlled by the control circuit so as to always be in an operating state, and the demultiplexed first and second demultiplexed light sources are provided. It is an optical amplification repeater circuit in which the pumping light amplifies each of the first and second optical amplification fibers.

A second feature of the present invention is an optical amplification repeater circuit in which the first and second pumping light sources in the first feature of the present invention are electrically connected in series with a single common control circuit. It is.

According to a third feature of the present invention, there is provided an optical amplifying repeater circuit in which the first and second pumping light sources according to the first feature of the present invention are electrically connected in parallel to a single common control circuit. It is.

[0017]

Since the optical amplification repeater circuit according to the present invention is configured as described above, the two optical outputs of the first pumping light source and the second pumping light source are demultiplexed by the optical multiplexer / demultiplexer. Thus, the first and second amplification optical fibers can be excited by the two split optical outputs, and even if one of the excitation light sources fails, the system does not become an obstacle.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. In the figure, β is the optical amplification repeater circuit of this embodiment, b,
b'is an optical fiber input to the demultiplexing fiber coupler,
3 ″ is a control circuit used for controlling the excitation light sources 2, 2 ′
Is an optical multiplexer / demultiplexer of a multiplexer / demultiplexer fiber coupler.

The same parts as those of the conventional example are designated by the same reference numerals. In this embodiment, the first excitation light source 2 and the second excitation light source 2
The pumping light source 2'is electrically connected in series and is driven and controlled by one control circuit 3 ".

Since the specifications of the present embodiment are such a concrete embodiment, since the semiconductor lasers which are the pumping light sources 2 and 2'are connected in series, the required current value is one. Of 500 to 700 mA will suffice. Therefore, as compared with the case where the pumping light sources 2 and 2'are connected in parallel, the feeding current I can be suppressed to 1 A or less at the maximum.

That is, the output lights La and La 'of the two pump light sources 2 and 2' are multiplexed and demultiplexed by the optical multiplexer / demultiplexer 10, and the first light is demultiplexed by the two demultiplexed pump lights Lb and Lb '. And the second E
It excites the r-doped fibers 1, 1 '. The optical multiplexer / demultiplexer 10 is usually called a "3 dB coupler",
Output light La, L entering from two input fibers b, b '
The a'is multiplexed by the optical multiplexer / demultiplexer 10 and is equally or ratio-adjusted to be split into two, which are emitted from the two output fibers a and a'as pump lights Lb and Lb '.

Therefore, even if the pumping light source 2 fails due to deterioration or the like, the output light La 'of the pumping light source 2' passes through the optical multiplexer / demultiplexer 10 to become the pumping light Lb, Lb ', and the two Er-doped fibers 1 , 1 ', the gains of the output signal lights L1' and L2 'are reduced as a result of the amplification of the input signal lights L1 and L2, but they are not absorbed as in the conventional example to cause a system failure.

If one of the pumping light sources 2 or 2 'fails, the control circuit 3 "is designed to increase the output of the other pumping light source 2 or 2', thereby preventing a decrease in gain. As described above, in the present embodiment β, since the pumping light sources 2 and 2 ′ are substantially redundant, it is not necessary to significantly increase the reliability of the pumping light sources 2 and 2 ′ as in the conventional case.

In this embodiment, the optical amplification relay circuit for driving the two pumping light sources in series is shown, but it goes without saying that parallel driving may be used if the power feeding capacity is sufficiently large. Alternatively, if an epoch-making reduction in the required current of the pumping light source is achieved in the future, the parallel operation of the pumping light source will be almost no problem, but even in that case, the constituent means of the present invention is very effective. .

[0025]

As described above, according to the present invention,
An optical amplification repeater circuit can be realized without requiring the pumping light source to have very high reliability, which is considered to be extremely difficult to achieve. Therefore, the effect of the present invention is extremely great for an optical amplification repeater system, especially for a long-distance system such as an optical submarine cable. The present invention increases the reliability of output light by operating a plurality of pump light sources at all times, and performs demultiplexing at a certain rate after demultiplexing output light, so that equal amplification gains can be obtained in the upstream and downstream directions.

Further, the method of simply arranging another non-operating pump light source which has been conventionally performed in a redundant configuration not only doubles the required number of light sources but also requires a redundant light source switching mechanism and the like. However, the present invention exhibits excellent usefulness in that it does not have such an adverse effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical amplification repeater circuit of the present invention.

FIG. 2 is a block diagram showing a basic optical amplifier circuit used conventionally.

FIG. 3 is a block diagram showing another embodiment of the same optical amplification circuit.

FIG. 4 is a block diagram showing a conventional optical amplification relay circuit configured using the optical amplification circuit of FIG.

[Explanation of symbols]

 A, B, B '... Optical amplification circuit α, β ... Optical amplification repeater circuit a, a', b, b '... Optical fiber 1, 1' ... Er-doped fiber 2, 2 '... Excitation light source 3, 3', 3 ″ ... Control circuit 4 ... Power supply circuit 5 ... Wavelength demultiplexing ratio demultiplexer 6, 6 '... Isolator 7, 7' ... Optical filter 8 ... Wavelength demultiplexing ratio demultiplexing fiber coupler 9 ... Feed line 10 ... Optical multiplexer / demultiplexer L1 , L1 ', L2, L2' ... transmission signal light I ... supply current La, La '... output light Lb, Lb' ... pumping light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Goto 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Kokusai Telegraph and Telephone Corp. (56) Reference JP-A-4-23528 (JP, A) JP-A-4-37729 (JP, A) JP-A-4-92483 (JP, A) JP-A-3-242053 (JP, A)

Claims (3)

(57) [Claims] An optical amplifying and repeating circuit for two-wire bidirectional optical communication for amplifying optical signals in a first direction and a second direction opposite to the first direction, respectively. The first and second optical amplification fibers for amplifying the signal lights respectively propagating in the two directions, the first and second pumping light sources, and the respective output lights of the first and second pumping light sources are combined. After the wave
One optical multiplexer / demultiplexer for demultiplexing into the first and second pumping lights respectively sent to the first and second optical amplification fibers, and a single unit for integrally controlling the outputs of the two pumping light sources A common control circuit and a power supply circuit for supplying electric power to the control circuit are provided, and the two first and second pumping light sources are controlled by the control circuit so as to be in an always operating state, and the demultiplexing is performed. An optical amplification repeater circuit, characterized in that the generated first and second pumping lights are respectively amplified by the first and second optical amplification fibers. 2. The optical amplification repeater circuit according to claim 1, wherein the first and second pump light sources are electrically connected in series with a single common control circuit. 3. The optical amplifying repeater circuit according to claim 1, wherein the first and second pump light sources are electrically connected in parallel to a single common control circuit.