JPH05268167A - Optical repeater - Google Patents

Abstract

PURPOSE:To provide the optical repeater with a small current consumption which is stably operated even when a current of each optical relay circuit being a load is fluctuated. CONSTITUTION:An inputted incoming line optical signal is subjected to reproduction relay or optical amplification relay at an optical relay circuit 6a and outputted to an optical fiber 3b. Similarly the inputted outgoing line optical signal is subjected to reproduction relay or optical amplification relay at an optical relay circuit 6b and outputted to an optical fiber 4b. On the other hand, the optical relay circuits 6a, 6b are connected in series, and a bypass circuit 8a bypassing part or all of the supplied current or the like is connected in parallel with each optical relay circuit 6a. A constant current source 9 is connected in series to plural optical relay circuit/bypass circuit pairs and they are connected as load circuits in parallel with a constant voltage diode 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical repeater for repeating an optical signal in an optical fiber transmission system.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional optical fiber relay transmission system. In the figure, 1a, 1b,
1c is an optical repeater, 2a, 2b, 2c and 2d are feeders,
3a, 3b, 3c, 3d and 4a, 4b, 4c, 4d are optical fibers, 5 is a constant current power source, and 24a, 24b are optical transmission terminal devices. In the optical fiber transmission lines 3 and 4 represented by the above 3a and 4a connecting the optical transmission terminal station devices 24a and 24b installed at the transmission end and the reception end, a large number of the above described 1a and the like are provided. The optical repeater 1 is inserted in series. Here, the power supply to each optical repeater 1 is usually performed by a constant current power supply method in which a direct current is supplied from a constant current power supply 5 installed at a transmitting end or a receiving end.

FIG. 5 is a block diagram showing the configuration of a conventional optical repeater. This figure shows "Undersea Light"
wave Communications (IEEE
press, 1986), page 384, FIG. 5 ”
In the figure, 1 is an optical repeater, 2
Reference numerals a and 2b are feeder lines, 3a, 3b, 4a and 4b are optical fibers, 6a and 6b are optical relay circuits, and 7 is a constant voltage diode. In addition, in FIG. 5, a supplement and a simplification are performed to facilitate understanding.

Next, the operation will be described. Optical repeater 1
Is composed of an upstream optical repeater circuit 6a, a downstream optical repeater circuit 6b, and a constant voltage diode 7. The upstream optical signal input through the optical fiber 3a is regeneratively relayed or optically amplified by the optical relay circuit 6a and output to the optical fiber 3b. Further, the downlink optical signal input through the optical fiber 4a is regeneratively relayed or optically amplified by the optical relay circuit 6b and output to the optical fiber 4b. On the other hand, the optical repeater circuit 6a and the optical repeater circuit 6b are connected to the constant voltage diode 7 in parallel with each other. The constant voltage diode 7 generates a predetermined constant voltage by the DC constant current input from the power supply line 2a, and the optical repeater circuits 6a and 6b.
Supply to. The details of the optical repeater circuit 6 are shown in FIG.
As shown in, the pumping light source 13 and the transistor 15 are connected in series. Although this form is standard, it was necessary to always apply a regular voltage to excite it in series connection.

[0005]

The conventional optical repeater is constructed as described above, and since each optical repeater circuit is connected in parallel to the constant voltage diode for generating the constant voltage, first of all, The number of the above optical repeater circuits, in this case, two circuits, that is, the upstream and downstream circuits, require twice the supply current. Further, since the bias current supplied to the laser diode (LD) used in each optical repeater circuit largely changes with temperature,
There is a problem that the voltage generated by the constant voltage diode varies.

In particular, when each optical repeater circuit is composed of a fiber type optical amplifier using a rare earth-doped optical fiber, the rare earth-doped optical fiber is used as a high-power pumping light source (usually a high-power LD is used). Since it had to be excited, the current consumption was large, and the power supply voltage fluctuation due to it was also large. Therefore, in order to economically realize an optical repeater system with stable performance, it was necessary to greatly reduce these.

The present invention has been made to solve the above problems, and provides an optical repeater which consumes less current and can realize stable operation even if the current of each optical repeater circuit as a load fluctuates. The purpose is to get.

[0008]

In an optical repeater according to the present invention, an optical repeater circuit that excites an input optical signal and a sidestream circuit that absorbs fluctuations in a power supply current due to excitation of the optical repeater circuit are first connected in parallel. Then, one set was connected in series and connected to a constant current source to form an optical repeater. More specifically, an optical repeater circuit that excites an input signal by an optical fiber, and a side that absorbs a change in the supply current for the excitation light source by the amount of light received by a light receiving element that receives a part of the excitation light source of the optical repeater circuit. The flow current control element is first connected in parallel to form a set, and when an overvoltage is further applied to the optical repeater circuit, a protection element for fully conducting this side current control element is provided, and the set connected in parallel is set. Multiple sets were connected in series and connected to a constant current power source to form an optical repeater.

[0009]

In the optical repeater according to the present invention, fluctuations in the feeding current of the optical repeater circuit are directly absorbed and shunted by the side-current control elements connected in parallel, and they are connected in series.
It becomes a constant current and flows through the optical repeater. When the voltage applied to the optical repeater circuit exceeds a certain voltage, the protection element becomes conductive, which makes the side-current control element conductive and a current flows.

[0010]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to FIG.
~ It demonstrates using FIG. FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1, 2, 2a, 2b, 3a, 3 are shown.
b, 4a, 4b, 6a, 6b and 7 are the same as those in FIG. Reference numerals 8a and 8b are sidestream circuits, and 9 is a constant current source.

Next, the operation will be described. Optical fiber 3
The upstream optical signal input by a is the optical repeater circuit 6a.
Regenerative repeater or optical amplifying repeater by the optical fiber 3b
Is output to. Further, the downlink optical signal input through the optical fiber 4a is regeneratively relayed or optically amplified by the optical relay circuit 6b and output to the optical fiber 4b. on the other hand,
The optical repeater circuit 6a and the optical repeater circuit 6b are connected in series with each other, and each optical repeater circuit 6a (or 6b) has a sidestream circuit 8a (or 8) that bypasses a part or all of the supplied current.
b) are respectively connected in parallel. A constant current source 9 is further connected in series to the two pairs of the optical relay circuit 6a (or 6b) / sidestream circuit 8a (or 8b), and these are connected in parallel as a load circuit to the constant voltage diode 7. Has been done.

As described above, since the optical repeater circuit 6a and the optical repeater circuit 6b are connected in series with each other, the DC constant current input from the feeder line 2a does not depend on the number of optical repeater circuits, that is, Only one circuit of current is needed instead of two circuits.
In addition, each optical repeater circuit 6a (or 6b) and the sidestream circuit 8a
Since the sum of the currents supplied to (or 8b) is always kept constant by the constant current source 9, the constant voltage diode 7 can be used even when the current consumption variation of the optical repeater circuit 6a (or 6b) is large.
The current flowing through is constant. Therefore, from the constant voltage diode 7, the optical repeater circuits 6a and 6b and the side current circuit 8a are connected.
Since the voltage supplied to (or 8b) is also constant, stable operation can be realized.

FIG. 2 is a block diagram showing an example of a detailed configuration of the optical repeater shown in the example of FIG. 1 applied to a case of an optical amplification repeater system using a rare-earth-doped optical fiber. is there. In the figure, 1, 2a, 2b, 3a, 3
b, 4a, 4b, 6a, 6b, 7, 8a, 8b and 9 are the same as those in FIG. 10a and 10b are rare earth-doped optical fibers, 11a and 11b are optical couplers, and 12a and 12
b is an optical directional coupler 13a, 14a is an excitation light source, 14
Reference numerals a and 14b are light receiving elements, transistors 15a and 15b are side current control elements, and 16a and 16b are current control circuits. Here, the optical repeater circuit 6a includes a rare earth-doped optical fiber 10a, an optical coupler 11a, an optical directional coupler 12a,
The optical repeater circuit 6b is composed of a pumping light source 13a and a rare earth-doped optical fiber 10b, an optical coupler 11b, an optical directional coupler 12b, and a pumping light source 13b. Further, the sidestream circuit 8a includes a light receiving element 14a and a transistor 15
a and the current control circuit 16a, the side current circuit 8
b is composed of a light receiving element 14b, a transistor 15b, and a current control circuit 16b. Compared with the conventional example, the pumping light source 14a and the drain transistor 15a which is a side current control element
Is connected in parallel. As a result, the pumping light source 14a can operate even with a relatively small applied voltage.

Next, the operation will be described. Although the optical repeater circuit 6a for the upstream line and the sidestream circuit 8a will be described below, the operations of the optical repeater circuit 6b for the downstream line and the sidestream circuit 8b are exactly the same. First, the operation of the optical repeater circuit 6a will be described. The rare earth-doped optical fiber 10a is, for example, a single-mode optical fiber having a length of several meters to several tens of meters doped with erbium, which is a rare earth element.
An optical coupler 11a is connected to the rare earth-doped optical fiber 10a. The excitation light source 13a has a wavelength of 1.48 μ, for example.
m semiconductor laser (LD), and its output light is input to the rare earth-doped optical fiber 10a by the optical coupler 11a. When the output light of the pumping light source 13a is input to the rare earth-doped optical fiber 10a, the rare earth-doped optical fiber 10a is in a population inversion state, and the upstream optical signal having a wavelength of 1.53 μm or 1.55 μm input by the optical fiber 3a. Is amplified by the stimulated emission effect and then output to the optical fiber 3b via the optical directional coupler 12a.

Next, the operation of the sidestream circuit 8a will be described. The side-current transistor 15a has a collector for the excitation LD.
An emitter of the anode 13a is connected to an emitter of the cathode 13a, and the sum of currents flowing through the exciting LD 13a and the transistor 15a is constantly kept constant by the current source 9. The light receiving current of the light receiving element 14a that receives a part of the output of the exciting LD 13a is input, and the output of the current control circuit 16a that controls the output current according to the amount of received light is connected to the base of the transistor 15a. Here, the current control circuit 16a keeps the optical output of the exciting LD 13a always constant by performing negative feedback control of the current of the transistor 15a so that the light receiving current of the light receiving element 14a is always constant. In this way, since the transistor 15a takes charge of only the applied voltage and only the fluctuation of the excitation current, the operation of the excitation current loss can be minimized.

Example 2. FIG. 3 shows an example of another detailed configuration of the current control circuit 16a shown in the embodiment of FIG. 2, and 7, 13a, 14a and 15a are the same as those in FIG. Reference numeral 17a is a constant current source, 18a and 19a are Darlington-connected transistors, 20a is a transistor, 21a and 22a are resistors, and 23a is a fault countermeasure circuit composed of N (N ≧ 1) diodes connected in series.

Next, the connection structure is shown below. LD1 for excitation
The light receiving element 14a that receives a part of the output light of 3a has an anode connected to the collector of the transistor 15a and a cathode connected to one end of a resistor 21a connected to the base of the transistor 18a. At the base of the transistor 18a, the resistor 21a and the negative terminal of the constant voltage diode 7 are provided.
Constant current source 17 for generating a reference current connected to the anode of the
The positive electrode terminal of a is connected. Also, the transistor 1
One end of a resistor 22a connected to the cathode of the constant voltage diode 7 is connected to the collector of 8a. The base of the transistor 20a is connected to the collector of the transistor 19a, the emitter is connected to the cathode of the constant voltage diode 7, and the collector is connected to the base of the transistor 15a and one end of the fault countermeasure circuit 23a. Further, the other end of the fault countermeasure circuit 23a is connected to the constant voltage diode 7. The current control circuit 16b can also be realized with a completely similar configuration. Here, in FIG. 3, the transistor 15a has an NPN.
This is a configuration example using a transistor, but when using a PNP transistor, the collector of the transistor 19a may be directly connected to the base of the transistor 15a without the PNP transistor 20a.

Next, the operation will be described using mathematical expressions. Here, each variable is defined as follows. Pout: Light output level of LDD 3a for excitation light source Iref: Reference current of constant current source 17a for generating reference current α: Photosensitivity of photodetector 14a β1: Darlington transistors 18a, 19a
Current amplification factor of the transistor 20a β3: current amplification factor of the transistor 15a β3: current amplification factor of the transistor 15a η: differential quantum efficiency of the LD 13a for the excitation light source Ild: DC bias current of the LD 13a for the excitation light source Ith: threshold current of the LD 13a for the excitation light source Ip : Light receiving current of the light receiving element 14a Itr: Collector current of the transistor 15a Ib: Current of the fault countermeasure circuit 23a It: Current of the constant current source 9

The following equation holds from FIG. It = Itr + Ild (1) pout = η · (Ild−Ith) (2) Itr = β1 · β2 · β3 · (Ip + Iref) + β3 · Ib (3) Ip = α · Pout (4) Expressions (1) to (1) From the equation (4), the optical output Pout during normal operation of the pump light source LD 13a is expressed by the following equation. Pout = [Iref + (It-Ith) / β1 ・ β2 ・ β3-Ib / β1 ・ β2)] / [α ・ {1 + 1 / (α ・ β1 ・ β2 ・ β3 ・ η)}] (5) LD13a for pumping light source Failure circuit 2 during normal operation
The current Ib flowing through 3a is about a leakage current and can be almost ignored.

Here, by designing so that β1 has a sufficiently large value by Darlington connection, the following (6),
Expression (7) is established. α ・ β1 ・ β2 ・ β3 ・ η >> 1 (6) β1 ・ β2 >> 1 (7) As a result, the equation (5) can be approximated by the following equation (8). Pout = Iref / α (8) From the above formula, the optical output Pout of the pump light source LD 13a is
By designing to suppress the fluctuation of the light receiving sensitivity α of the light receiving element 14a, the fluctuation of the optical output due to the temperature change of the differential quantum efficiency η and the threshold current 1th of the excitation light source LD 13a is suppressed and is determined by the reference current Iref. It can be seen that it can be controlled to a predetermined constant value.

The anode of the LD 13a for the excitation light source-
When an open failure occurs between the cathode terminals, the N (N ≧ 1) series-connected diodes that constitute the failure countermeasure circuit 23a are designed to be turned on. At this time, the collector current Itr of the transistor 15a is saturated. Is expressed by the following equation (9). Itr = β3 · Ib = It (9) That is, even when the pump light source LD 13a has an open failure, the total current It defined by the constant current source 9 can be shunted to the transistor 15a, and the other It is possible to prevent the optical output of the optical repeater circuit 16b from being interrupted.

Reference current Ir of the optical repeater having the above structure
FIG. 4 shows an actual measurement example of the relationship between ef and the average optical output power Pout of the LD for the excitation light source. Here, P1 and P2 are the current Ire of the constant current source 17a for generating the reference current in the side current circuit 8a.
The light outputs of the excitation light source LDs 13a and 13b when f is changed are shown. From FIG. 4, LD13a for excitation light source
Optical output P1 of the other pumping light source LD13 changes in proportion to the reference current Iref and has any value.
It can be seen that it does not affect the light output of b.

In the above embodiment, the optical repeater circuit goes up,
Although the case of a total of two downlink devices has been described, the same function can be realized with the same configuration even when the number of devices is further increased, such as in the case of considering a backup device. Moreover, although the case where the pumping direction of the pumping light input to the rare earth-doped optical fiber is opposite to the signal light has been described, the same effect is obtained even when the pumping light is in the same direction.

[0024]

As described above, according to the present invention, the optical repeater circuit and the side-current circuit that absorbs the fluctuation of the feeding current due to the excitation of the optical repeater circuit are first connected in parallel to form a set, and these Since it is configured to connect multiple sets to a constant current source, the same current consumption as in the case of one optical repeater circuit is required even if there are multiple optical repeater circuits, and supply to each optical repeater circuit and side-current circuit is possible. Since the sum of the currents is kept constant, there is an effect that the total power consumption is small and a stable operation can be realized even if the current consumption of the optical repeater circuit fluctuates.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a detailed configuration example of an optical repeater circuit and a sidestream circuit of an optical repeater according to an embodiment of the present invention.

FIG. 3 is a configuration diagram showing a detailed configuration example of a current control circuit of an optical repeater according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the reference current of the optical repeater and the average optical output power of the pumping light source according to the embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional optical repeater.

FIG. 6 is a configuration diagram showing an example of application in a conventional optical repeater system.

[Explanation of symbols]

1a, 1b, 1c Optical repeater 2a, 2b, 2c, 2d Feed line 3a, 3b, 3c, 3d Optical fiber 4a, 4b, 4c, 4d Optical fiber 5 Constant current power source 6a, 6b Optical repeater circuit 7 Constant voltage diode 8a , 8b Side current circuit 9 Constant current source 10a, 10b Rare earth doped optical fiber 11a, 11b Optical coupler 12a, 12b Optical directional coupler 13a, 14a Excitation light source 14a, 14b Photodetector 15a, 15b Transistor 16a, 16b Current control circuit 17a Constant current source 18a, 19a Darlington connected transistor 20a Transistor 21a, 22a Resistor 23a Fault countermeasure circuit 24a, 24b Optical transmission terminal device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location H04B 3/44 9199-5K (72) Inventor Koji Goto 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo No. International Telegraph and Telephone Corporation (72) Inventor Ken Matsushita 5-1-1 Ofuna, Kamakura-shi Mitsubishi Electric Corp. Communication Systems Research Laboratories (72) Inventor Tadanori Kitayama 5-1-1 Ofuna, Kamakura-shi Mitsubishi Electric Corporation Company Communication Systems Laboratory

Claims (3)

[Claims] 1. An optical repeater circuit that excites an input optical signal to reproduce or amplify and repeat it and a sidestream circuit that absorbs fluctuations in a feeding current of the optical repeater circuit are connected in parallel to form a set, and the optical repeater circuit and the optical repeater circuit are combined. An optical repeater in which a plurality of sets of sidestream circuits are connected in series to form an optical repeater, and a constant current source is connected to the optical repeater. 2. An optical repeater circuit for exciting and regenerating or amplifying and repeating an input signal by an optical fiber, and a change in the power supply current for excitation by the amount of light received by a light receiving element that receives a part of an excitation light source of the optical repeater circuit. And a side current control element that absorbs the current are connected in parallel to form one set, and a plurality of the optical repeater circuit and one set of the side current control element are connected in series to form an optical repeater. Optical repeater with source connected. 3. An optical repeater circuit for exciting and reproducing or amplifying and repeating an input signal from an optical fiber, and a side current control element described later are connected in parallel to form a set, and a part of an excitation light source of the optical repeater circuit. The side flow current control element that absorbs the change in the power supply current for excitation is controlled by the amount of light received by the receiving light receiving element, and the side flow current control element is made conductive when an overvoltage is applied to the exciting optical relay circuit. An optical repeater in which a protection element is provided as a side-current control circuit, a plurality of sets of the optical repeater circuit and a side-current control element are connected in series to form an optical repeater, and a constant current source is connected to the optical repeater. ..