JPH05190946A - Excitation light supply method - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a pumping light supply method having two pumping light supply means for directly amplifying an optical signal incident on an erbium-doped optical fiber by injecting the pumping light. There is provided a pumping light supply method for detecting deterioration of the first LD and switching to the second LD, and eliminating the influence on the communication line due to the switching. [Structure] A pumping light supply method includes a first pumping light supply means 20, a second pumping light supply means 30, a storage means 40, and deterioration detection.
The switching device 50 and the switching device 50 deteriorate the emission amount of light emitted by the drive current flowing through the LD of the first excitation light supply device 20 and the emission amount of the initial state corresponding to the same drive current stored in the storage device 40. When the detection / switching means 50 compares and detects deterioration of a set value or more, the pumping light output is supplied from the first pumping light supply means 20 to the second pumping light supply while maintaining the pumping light output at a constant level. It is configured to switch to the means 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying pumping light to a laser diode (hereinafter referred to as an LD) of an optical direct amplifier used for digital and analog optical transmission lines, and deterioration detection.

Recently, an optical direct amplifier using an erbium-doped optical fiber is being developed as a repeater system for an optical transmission line. When this optical direct amplifier is put into operation, like the conventional optical amplifier that converts an optical signal into an electric signal and amplifies it, it is used when the LD of the first pumping light supply means deteriorates after being operated for a long time. In switching to the second pumping light supply means, a stable pumping light supply method that does not affect the operation line is required.

[0003]

2. Description of the Related Art FIG. 5 shows an example of an IL curve of a conventional optical amplifier which converts an optical signal into an electric signal and amplifies it. 6 shows an example of a conventional optical direct amplifier.

As shown in FIG. 5, in the case of a conventional optical amplifier which converts an optical signal into an electric signal and amplifies the electric signal, a bias current of the LD is always supplied to increase the bias current compared with an initial value. Therefore, the deterioration was detected.

Further, there are two conventional first and second conventional ones shown in FIG.
The switching from the first LD 21 to the second LD 31 in the pumping light supply method of the optical direct amplifier having the LDs 21 and 31 is performed when the optical output from the first LD 21 is cut off. The ALC 71, which has received the electric signal obtained by converting the optical signal extracted by the wave filter 12 by the O / E converter 81, detects that the optical output of the first LD is off, and operates the LD drive circuit 32. And the second L
The method of stopping the operation of the first LD 21 by stopping the operation of the LD drive circuit 22 while operating the D31 has been adopted.

[0006]

In the optical direct amplification using the erbium-doped optical fiber, a constant direct current is always applied to the LD for supplying the pumping light, which is similar to the LD of the conventional optical amplifier. Since there is no such bias current, the deterioration of the LD cannot be detected by the method such as the conventional optical amplifier.

Further, in the conventional switching from the first LD to the second LD in the optical direct amplifier having the first and second LDs, the LD output interruption is detected and the switching is performed. A large signal loss may occur. Especially in international submarine optical communications that transmit a large capacity, the effect is extremely large.

The present invention is to solve such a problem. Instead of detecting disconnection of the first LD and switching to the second LD, deterioration of the first LD is detected and the second LD is detected. It is an object of the present invention to provide a method of supplying excitation light for excitation light, which is characterized by switching to

[0009]

FIG. 1 is a block diagram showing the principle of an excitation light supply method according to the present invention. In the figure, 20 is the first
Excitation light supply means, 30 is second excitation light supply means, 40
Is a storage means, 50 is a deterioration detection / switching means, and 90 is an erbium-doped optical fiber.

The present invention is provided with first and second pumping light supply means 20 and 30 having first and second LDs, to which the drive control voltage is applied. In the pumping light supply method for amplifying the signal light, the pumping light is transmitted from 20 and is multiplexed with the signal light to be amplified and is incident on the erbium-doped optical fiber 90. A storage unit 40 that stores a curve of the drive current of the first LD vs. the light emission amount, and that can extract the light emission amount corresponding to the applied drive current of the first LD, and the first excitation light supply unit. 20
The drive control signal is applied when it is detected that the amount of light emitted by the first LD is deteriorated by a set amount or more as compared with the amount of light emitted from the first LD stored in the storage unit 40 in the initial state. A deterioration detecting / switching means 50 is provided for switching from the first pumping light supply means 20 to the second pumping light supply means 30.

When it is detected that the amount of light emitted by the first excitation light supply method 20 has deteriorated beyond a set amount,
The supply of the excitation light is switched from the first excitation light supply means 20 to the second excitation light supply means 30.

Further, an erbium-doped optical fiber 90
The object can be achieved by equipping the optical direct amplifier using the above with the pumping light supply circuit according to the pumping light supply method of the present invention.

[0013]

The present invention is based on the erbium-doped optical fiber 90.
In the pumping light supply method, the pumping light supply method includes first pumping light supply means 20 for injecting pumping light and second pumping light supply means 30 for directly amplifying the signal light incident on the first pumping light supply. When it is detected that the LD of the means 20 has deteriorated and the drive current of the LD has increased, and the quantity of light emitted has deteriorated by a set amount or more as compared with the amount of light emission in the initial state, it is switched to the second excitation light supply means 30. is there.

According to the present invention, the first excitation light supply means 2
The storage means 40 for storing the I-L characteristic at the time of manufacture of 0 is provided, and the drive current flowing in the LD of the first excitation light supply means 20 and the amount of light emission at that time are monitored and correspond to the drive current at that time. I-L in the initial state stored in the storage means 40
When the deterioration of the LD of the first pumping light supply means 20 is detected by comparing the light emission amount in the curve, the deterioration detection / switching means 50 for switching the driving current of the LD to the first pumping light supply means 30. Set up.

The LD of the first excitation light supply means 20
Deteriorates, the drive current required to obtain a constant light emission amount increases. However, the light emission amount emitted by the current drive current value and the storage means 40 corresponding to the same drive current value.
The deterioration detection / switching means 50 compares the amount of light emitted from the first excitation light supply means 20 in the initial state on the IL characteristic, and if there is a decrease in the amount of light emission equal to or greater than the set value, the deterioration is caused. By detecting as, it is possible to automatically switch the supply of the excitation light from the first excitation light supply means 20 to the second excitation light supply means 30.

Further, by providing the pumping light supply circuit of the optical direct amplifier with the pumping light supply method of the present invention, the optical direct amplifier can be stably operated for a long period of time.

[0017]

EXAMPLES Next, examples will be described with reference to FIGS. 2 and 3. 2 is an embodiment of the present invention, and FIG. 3 is a diagram for explaining the operation of FIG.
The corresponding curve of the drive current flowing through the LD and the light emission amount of the LD) is shown.

In the figure, the same reference numerals as those in FIG.
Reference numeral 12 is an optical demultiplexer, and 21 is the first pumping light supply means 2 of FIG.
LD constituting 0, 22 is an LD drive circuit constituting the first pumping light supply means 20 of FIG. 1, 31 is an LD constituting the second pumping light supply means 30 of FIG. 1, 32 is the LD of FIG. 1. The LD drive circuit constituting the excitation light supply means 30 of FIG.
1 is a voltage generation circuit as an implementation example of the storage means 40, 51 is a comparison circuit as an implementation example of the deterioration detection / switching means 50 in FIG. 1, and 61 is an implementation example of the deterioration detection / switching means 50.
A switch 71 is an automatic level control circuit ALC (Autom).
atic Level Control), 81 is O /
It is an E converter. Note that a to d'in FIG. 2 correspond to a to d'in FIG.

Usually, as the excitation light, the first LD 21 is driven by the LD drive circuit 22 and, for example, 1.48 μm.
Of the pumping light is output, passes through the optical coupler 13 and the optical multiplexer 11, enters the erbium-doped optical fiber 90, and amplifies the signal light incident from the transmitting side, for example, the signal light of 1.55 μm.

In the optical demultiplexer 12, a part of the signal light amplified by the erbium-doped optical fiber 90 is separated and taken out, and is further converted into an electric signal by the O / E converter 81. This electric signal is received by the ALC71,
The LD drive current control voltage is level-adjusted and sent so that the level of the signal light in the optical demultiplexer 12 is constant, and sent to the LD drive circuit 22 via the switch 61.

As shown in FIG. 3, when the operation period becomes long, the first LD 21 gradually deteriorates as the I-L curve was initially the AB curve.
The curve becomes like an A′-B ′ curve, and in order to obtain the same light emission amount, the LD drive current increases and the slope becomes gentle.

Here, the value of the AB curve in the initial state is stored in the voltage generating circuit 41 to obtain a certain light emission amount (= b in FIG. 3) and its light emission amount during operation at all times. The comparison circuit 51 compares the amount of light emitted in the initial state (= b ′ in FIG. 3) that emits light at the required LD drive current value (a in FIG. 3), and when the difference exceeds the set value, When the LD needs to emit light strongly and a large drive current has to flow, if the drive current exceeds a predetermined value (c in FIG. 3), it is detected as deterioration and pumping light is sent to the switch 61. First LD 21 to second LD 31
The LD drive switching command is sent to switch to.

When this LD drive switching command is transmitted, the pumping light is not switched from the first LD 21 to the second LD 31 at once, but the optical signal level of the optical demultiplexer 12 is always kept constant. While ALC71 adjusts the level,
The ALC 71 and the switch 61 are configured so that the load is gradually transferred from the first LD 21 to the second LD 31 and switched.

FIG. 4 is a specific example of the voltage generating circuit 41 in FIG. 2 and shows a memory circuit for storing the IL characteristic at the time of manufacturing the LD. In the figure, 42 is an operational amplifier, 43 and 45 are variable resistors, and 44 is a resistor, which is a circuit for storing the I-L curve at the time of obtaining the I-L curve after manufacturing the LD. By inputting the LD drive current signal (I) to the + input terminal of the operational amplifier 42 by adjusting the inclination of the IL curve with the resistor 45 and adjusting the offset voltage which is the absolute value of the curve with the variable resistor 43. , A voltage corresponding to the light emission amount (L) of the IL curve is obtained at the output.

[0025]

As described above, according to the present invention,
Since the LD drive current increases as the LD in operation deteriorates, when the drive current required to obtain a constant light emission amount exceeds a certain value, the first LD automatically changes to the second LD. Of course, since the supply of the pumping light is gradually switched, it is possible to smoothly switch the line of any large capacity without affecting the line.

In particular, in a system such as an international undersea optical communication system in which a large number of optical amplifiers are used in the middle of a long distance, it is possible to completely eliminate the influence of LD switching on the line. Therefore, the reliability of the communication line can be significantly improved.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a pumping light supply method for an optical communication system according to the present invention.

FIG. 2 is a diagram showing an example of the present invention.

FIG. 3 is an operation explanatory diagram of FIG. 2;

FIG. 4 is a diagram showing a specific example of the voltage generating circuit in FIG.

FIG. 5 is a diagram showing an IL curve of a conventional optical amplifier.

FIG. 6 is a diagram showing an example of a conventional optical direct amplifier.

[Explanation of symbols]

 11 optical multiplexer 12 optical demultiplexer 13 optical coupler 20, 30 first and second pumping light supply means 21, 31 first and second LD 22, 32 LD drive circuit 40 storage means 41 voltage generation circuit 42 operational amplifier 43, 45 Variable resistance 44 Resistance 50 Deterioration detection / switching means 51 Comparison circuit 61 Switching device 71 Automatic level control circuit (ALC) 81 O / E converter 90 Erbium-doped optical fiber

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04B 10/16

Claims (2)

[Claims] 1. A first and second excitation light supply means (20, 30) having first and second laser diodes are provided, and the first excitation light supply to which a drive control voltage is applied. The pumping light is sent from the means (20) and is multiplexed with the signal light to be amplified, and the erbium-doped optical fiber (9
In the pumping light supply method for amplifying the signal light by making incident on (0), the curve of the driving current vs. the light emission amount of the first laser diode in the initial state in which the characteristics are not deteriorated is stored and applied. The storage means (40) capable of extracting the light emission amount in the initial state corresponding to the driving current of the first laser diode, and the light emission amount emitted by the first excitation light supply means (20) are the storage means (40). ), When it is detected that the first laser diode has deteriorated by a set amount or more as compared with the light emission amount in the initial state, the drive control signal is applied to the first excitation light supply means. Degradation detection / switching means (50) for switching from (20) to the second excitation light supply means (30) is provided, and the light emission amount of the first excitation light supply method (20) is equal to or more than the set amount. When it is detected that the phased, from the supply of excitation light the first pumping light supply means (20), pumping light supply method that features that switching to the second pumping light supply means (30). 2. Erbium-doped optical fiber (90)
The pumping light supply method according to claim 1, further comprising: an optical direct amplifier for directly amplifying the signal light by using.