KR20020094815A - Duplex optical amplifier in duplex optical line pair - Google Patents

Abstract

PURPOSE: A duplex optical amplifier in duplex optical line pair is provided to simultaneously amplify optical signals of the duplex optical line pair using one optical amplifier. CONSTITUTION: Circulators(111,112) input and output two optical signals progressed to inter-different directions. Wavelength selection couplers(113,114) couples the optical signals inputted through the circulators(111,112) with pump lights generated in pump sources(115,116). An optical fiber(117) amplifies the inputted duplex optical signals. The circulators(111,112) adds the optical signals progressed from front and rear ends of the optical fiber(117) to two optical lines.

Description

Duplex Optical amplifier in Duplex Optical line pair

In the present invention, in the wavelength division multiplexing, in particular, a bidirectional optical line capable of simultaneously optically amplifying optical signals of two lines using a single optical amplifier in a duplex optical line pair composed of two optical lines. A bidirectional optical amplifier in a pair.

Wavelength-division multiplexing (WDM) optical transmission systems can increase the capacity to transmit on a single fiber by increasing channels of different wavelengths.

The optical transmission system is an erbium-doped optical amplifier (EDFA), in particular, the main driving force for the development of the optical transmission system. EDFAs play an important role in amplifying the strength of weakened optical signals through the process of transmission, wavelength branching / combining, and multiple / inverse multiplexing in optical transmission systems. They are applied to a wide range of preamplifiers, post amplifiers, and line amplifiers. It is becoming.

In the conventional optical transmission system, as shown in FIG. 1, the lower channel transmitter and the lower channel receivers 11 and 12, the upper channel transmitter and the upper channel receivers 21 and 22, and the multiplexing and demultiplexer (MUX / DEMUX) 13, 14, 23, 24, and optical amplifiers 15, 25.

Here, the optical amplifiers 15 and 25 include a front and rear for blocking the light flowing back around the front and rear ends of the optical fibers (EDF) 15e and 25e doped with erbium as an amplification medium and the optical fibers 15e and 25e. Isolator 15a, 15b, 25a, 25b, wavelength selective couplers 15c, 25c for injecting respective pump lights into optical fibers 15e, 25e, and forward pump light sources 15d, 25d, respectively. .

The optical transmission system as described above will be described with reference to FIG. 1.

First, the channel signals lambda _1, lambda_2, lambda_3, and lambda_4 transmitted from the lower channel transmitters TX # 1 to TX # 4 11 are multiplexed by the multiplexer 13, and the multiplexed optical signal is the first signal. After being amplified by the optical amplifier 15, demultiplexed by the demultiplexer 14 and the transmitted channel signal is input to the lower channel receiver 12, respectively.

Here, the optical signal input to the first optical amplifier 15 is input to the wavelength selective combiner 15c through the shear isolator 15a, and the pump light emitted from the pump light source 15d by the wavelength selective combiner 15c. And the input optical signal are combined to enter the optical fiber 15e. The incident pump light excites the erbium ions in the ground state in the optical fiber, and the optical signal is amplified by the induced emission of the excited erbium ions. The optical signal amplified by the optical fiber is output through the rear end isolator 15b.

When the first optical amplifier 15 outputs the amplified optical signal through the rear stage isolator 15b, the first optical amplifier 15 is demultiplexed by the demultiplexer 14 and is provided to the lower channel receivers RX # 1 to RX # 4 12. Each channel signal λ _1, λ_2, λ_3, λ_4 is received.

Meanwhile, each channel signal transmitted from the upper channel transmitters TX # 1 to TX # 4 is multiplexed by the multiplexer 24, and the multiplexed channel optical signal is amplified by the second optical amplifier 25 and then reversed. It is demultiplexed by the multiplexer 23 and received by each channel receiver of the upper channel receivers RX # 1 to RX # 421, respectively.

Here, the second optical amplifier 25 is coupled to the optical fiber 25e after the optical signal input through the shear isolator 25a is combined with the pump light from the pump light source 25d at the wavelength selective combiner 25c. . The optical signal incident on the optical fiber 25e is amplified and then output to the demultiplexer 23 through the rear end isolator 25b.

In this case, the isolators 25a and 25b block the light flowing backwards around the front and rear ends of the optical fiber 25e.

In order to amplify the optical signal passing through the optical line, the optical amplifiers 15 and 25 convert the energy of the optical signal from each of the pump light sources 15d and 25d into an input transmission optical signal and then amplify the long distance transmission. Makes this possible. In the bidirectional optical line pair, two optical amplifiers 15 and 25 may be used to amplify the two lines.

However, the optical amplifiers 15 and 25 are important for stability so that the isolators 15a and 15b transmit light in only one direction to prevent the optical amplifier from escaping from the steady state due to reflection of the transmission optical signal. By using 25a and 25b respectively, only unidirectional amplification is supported. That is, when performing bidirectional amplification, there is a problem that optical amplifiers 15 and 25 must be used in respective transmission directions.

Disclosure of Invention The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a bidirectional optical amplifier in an optical line pair that can simultaneously amplify an optical signal of a bidirectional optical line pair using one optical amplifier. There is this.

In addition, the purpose of the present invention is to provide a bidirectional optical amplifier in a pair of bidirectional optical line pairs by using a circulator instead of an existing isolator to increase the input / output ports of the optical amplifier to amplify two optical signals in different directions. .

It is another object of the present invention to provide a bidirectional optical amplifier in a pair of bidirectional optical lines which can extinguish the reflected optical signal when outputting the optical signal amplified by the optical fiber to the circulator.

It is still another object of the present invention to provide a bidirectional optical amplifier in a bidirectional optical line pair capable of amplifying an optical signal for an optical signal traveling in both directions in one optical amplifier.

1 is a block diagram of an optical transmission system using a unidirectional optical amplifier of a conventional unidirectional optical line.

2 is a block diagram of an optical transmission system using a bidirectional optical amplifier in a bidirectional optical line pair according to an exemplary embodiment of the present invention.

3 is a detailed block diagram of a bidirectional optical amplifier in a bidirectional optical line pair according to an embodiment of the present invention.

4 is a signal flow diagram of a circulator applied to an embodiment of the present invention.

5 is a block diagram of a bidirectional optical amplifier in a bidirectional optical line pair according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

11,101 ... sub-channel transmitter 12,102 ... sub-channel receiver

13,24,103,108 ... Multiplexer14,23,104,107 ... Demultiplexer

21,105 ... high channel receiver 22,106 ... high channel transmitter

15,25,110 ... optical amplifier 15a, 15b, 25a, 25b ... isolator

15c, 25c, 113,114 ... wavelength selector

15d, 25d, 115,116 ... pump light source15e, 25e, 117 ... optical fiber

111,112 ... Circulator

To achieve the above object, a bidirectional optical amplifier in a bidirectional optical line pair according to the present invention,

A plurality of circulators for inputting and outputting two optical signals traveling in different directions at both ends, a wavelength selective combiner for coupling the optical signals input to the circulators with the pump light generated from the pump light source, and incident bidirectional And optical amplifying means made of optical fibers for amplifying the optical signal.

Preferably, the circulator combines an optical signal traveling through two optical lines into an optical amplifier.

In detail, the circulator includes first input / output means for receiving a first channel transmission optical signal input from one optical line and outputting the first optical signal to a second port to amplify the optical fiber, and the amplified input to the second port. And second input / output means for outputting the optical signal to the third port for transmitting the optical signal as a channel transmission optical signal of another optical line.

Preferably, the circulator outputs an optical signal amplified by the optical fiber and extinguish the reflected signal among the output optical signals.

Preferably, the optical amplifying means is a bidirectional optical amplifying means, and the optical amplifying means is characterized by using one optical fiber.

Hereinafter, with reference to the accompanying drawings as follows.

2 is a block diagram of an optical transmission system using a bidirectional optical amplifier in a bidirectional optical line pair according to an embodiment of the present invention, and FIGS. 3 and 5 are views of a bidirectional optical amplifier in a bidirectional optical line pair according to an embodiment of the present invention. 4 is a detailed flowchart illustrating a signal flow of an optical circulator applied to an embodiment of the present invention.

2 and 3, the lower channel transmitter 101 and the lower channel receiver 102, the upper channel transmitter 105 and the upper channel receiver 106, and the multiplexing and demultiplexing channel optical signals The multiplexer and the demultiplexer (103, 108, 104, 107) and the bi-directional optical amplifier 110 for amplifying the multiplexed optical signal of the lower channel and the upper channel input in different directions and outputs to the demultiplexer.

The bidirectional optical amplifier 110 transmits the multiplexed signal to the optical fiber at the front and rear ends, and outputs the optical signal amplified from the optical fiber to the demultiplexers 104 and 107 and dissipates the reflected signal. 2 circulator (111, 112), the wavelength selective coupler (113, 114), the pump light source (115, 116), characterized in that it comprises an optical fiber 117, which is an erbium doped amplification medium.

Here, the wavelengths of the channels transmitted from the left end of the optical fiber 117 to the right end of the optical fiber 117 and from the right end of the optical fiber 117 to the left end of the optical fiber 117 are different.

Referring to the accompanying drawings, a bidirectional optical amplifier in a bidirectional optical line pair according to an embodiment of the present invention configured as described above is as follows.

First, referring to FIG. 2, the channel signals λ _1, λ_2, λ_3, and λ_4 are respectively multiplexed from the lower channel transmitters TX # 1 to TX # 4 101 through a multiplexer (MUX) 103. The multiplexed optical signal is amplified by the optical amplifier 110, and the amplified optical signal is demultiplexed by the demultiplexer (DEMUX) 104, and then the lower channel receivers RX # 1 to RX # 4 102 The corresponding channel signals of λ _1, λ_2, λ_3, and λ_4 are input.

The upper channel signals λ _ 5, λ_6, λ_7, and λ_8 output from the upper channel transmitters TX # 1 to TX # 4 106 are multiplexed by the multiplexer 108, and the multiplexed optical signal is optically transmitted. The amplified optical signal is demultiplexed by the demultiplexer 107 and then the upper channel signals λ _5 and λ_6 of the upper channel receivers RX # 1 to RX # 4. , λ_7 and λ_8).

As such, two input optical signals transmitted in different directions in two bidirectional optical line pairs are amplified using one optical amplifier 110 and output to the corresponding output path.

To this end, the optical amplifier 110 includes first and second circulators 111 and 112, wavelength selective couplers 113 and 114, pump light sources 115 and 116, and optical fibers 117.

The pump light sources 115 and 116 are bidirectional pump light sources, and the wavelength selective couplers 113 and 114 and the pump light sources 115 and 116 are located symmetrically to the optical fiber. If the pump light source is applied in only one direction, the degree of amplification of the optical signal traveling in different directions may be different. This amplification difference can be compensated for by optimizing the optical amplifier according to the power of the pump light source and the data signal.

That is, the optical amplifier is classified into forward pumping, reverse pumping, and bidirectional pumping according to the relative directionality of the data signal and the pump light source. Since the optical amplifier has relative advantages and disadvantages, it may vary depending on the optical amplifier design method.

The first and second circulators 111 and 112 are optical elements having three input / output ports, and an optical signal input to the first port is a second port, and an optical signal input to a second port is a third port. Play a role

As shown in FIG. 3 and FIG. 4A, the first circulator 111 is provided at the left end of the optical fiber 117 to remove the lower channel optical signal S1 _In multiplexed by the multiplexer 103. It is input to the first port P1 and output to the second port P2.

The optical signal S1 _In output to the second port P2 of the first circulator 111 is combined with the pump light generated in the first pump light source 115 by the first wavelength selective combiner 113. The light signal incident on the optical fiber 117 is amplified by the optical fiber 117 and then output through the second circulator 112. In addition, the first circulator 111 receives an optical signal S2 _Out output from the right end of the optical fiber 117 to the left end and outputs it to the second port P2 to the third port P3.

At this time, the optical signal S2 _Out output to the third port P3 of the first circulator 111 is demultiplexed by the demultiplexer 107 and input to the upper channel receiver 105. The first circulator The first circulator 111 dissipates the back reflected signal S3 _In among the optical signals S2 _Out output through the third port P3 of the 111, thereby providing an optical fiber ( The reflected light signal is not input to 117.

As shown in FIGS. 3 and 4B, the second circulator 112 is provided at the right end of the optical fiber 117. When the lower channel signal is multiplexed and input from the multiplexer 108, the input optical signal is inputted. S2 _In is input to the first port P1 and output to the second port P2.

The optical signal S2 output to the second port P2 of the second circulator 112 is combined with the pump light generated from the pump light source 116 in the second wavelength selective coupler 114 and then the optical fiber 117. ), The optical signal incident on the optical fiber 117 is amplified and then output (S2 _out ) through the first circulator 111.

In addition, the second circulator 112 receives the optical signal S1 amplified by the optical fiber 117 and inputs it to the second port P2 and outputs it to the third port P3, and the port P3. The signal output as is demultiplexed by the demultiplexer 104 and is output to the lower channel receiver 102.

At this time, the back reflected signal S3 of the optical signal S1 output through the third port P3 of the second circulator 112 disappears from the second circulator 112. As a result, it does not enter the optical fiber 117.

The optical fiber 117 excites the incident optical signal by the pump light source 115 to excite the erbium ions in the ground state in the optical fiber 117, and the optical signal is amplified by the induced emission of the excited erbium ions. One optical fiber 117 amplifies and outputs optical signals input in different directions.

As shown in FIG. 5, a signal propagated to two optical lines in opposite directions is amplified by one optical amplifier 110, and two optical lines are routed from the circulators 111 and 112 at the front and rear ends of the optical fiber. It combines the input and output optical signals into a single optical amplifier.

In the conventional two-way transmission system, an optical amplifier is provided in each of them and optically amplifies a signal traveling only in one direction. However, the present invention applies a bidirectional transmission system using one optical amplifier 110.

In addition, the optical amplifier 110 having the circulators 111 and 112 as described above may have two input terminals and output terminals, and of course, the optical signal inputted to each input terminal is again amplified into the optical amplifier. It can be prevented from being reflected back, so as not to impair the stability of the optical amplifier.

The optical amplifier 110 can replace two optical amplifiers in a transmission environment, and can be used to amplify two transmission lines simultaneously with only one optical amplifier, and amplify the optical signal by inputting a transmission signal in both directions to one optical fiber. To make it possible.

As described above, according to the bidirectional optical amplifier applied to the bidirectional optical line pair according to the present invention, it is possible to simultaneously optically amplify the optical signals of the two lines by using one optical amplifier in the bidirectional optical line pair, By reducing the number of expensive optical amplifiers, the cost of the transmission system can be reduced.

Claims (4)

A plurality of circulators for inputting and outputting two optical signals traveling in different directions, a wavelength selective combiner for coupling the optical signal input through the circulator with the pump light generated from the pump light source, and an incident bidirectional optical signal A bidirectional optical amplifier in a bidirectional optical line pair, characterized in that it comprises an optical amplification means made of optical fibers for amplifying. The method of claim 1, The circulator is a bidirectional optical amplifier in a bidirectional optical line pair, characterized in that to combine the optical signal traveling in two optical lines in the front and rear ends of the optical fiber to the optical amplifier. The method of claim 1, The circulator may include first input / output means for receiving a channel optical signal through a first port and outputting the optical signal amplified by the optical fiber through a first port, and outputting the third optical signal through the second port. A bidirectional optical amplifier in a bidirectional optical line pair, comprising two input and output means. The method of claim 1, And said circulator outputs an optical signal amplified by the optical fiber and extinguish the reflected signal among the output optical signals.