JP5270858B2 - Single-core bidirectional optical transmission system, single-core bidirectional optical amplifier, and single-core bidirectional optical transmission method used therefor - Google Patents

Description

  The present invention relates to a single-core bidirectional optical transmission system, a single-core bidirectional optical amplifier, and a single-core bidirectional optical transmission method used therefor, and in particular, a single-core bidirectional optical fiber transmission that performs bidirectional transmission using a single-core optical fiber. The present invention relates to a single-core bidirectional optical amplifier that performs batch amplification of bidirectional optical signals with a single optical amplifier.

  In the single-core bidirectional optical transmission technology that performs bidirectional transmission with one optical fiber, the optical fiber to be used is ½ compared to the two-core bidirectional transmission in which each of the two fibers performs unidirectional transmission. Therefore, when laying a new optical fiber, the laid fiber is ½, and when using a dark fiber, the fiber usage fee is ½, so an economical system can be constructed. is there.

  In optical communication, optical signals attenuated due to transmission path loss using an optical amplifier to realize long-distance transmission without optical / electrical (O / E) conversion and electric / optical (E / O) conversion. The light is amplified. The optical amplifier has features such as the ability to collectively amplify wavelength-multiplexed signals independent of the bit rate and signal format, and can realize a flexible and low-cost network.

  In general, an erbium-doped fiber amplifier that amplifies signal light by making excitation light incident on the erbium-doped fiber together with signal light is used as an optical amplifier. This optical amplifier is designed to amplify light transmitted in one direction, and its configuration is not so complicated. Therefore, it is not possible to simply insert an optical amplifier in a single-core bidirectional transmission path in which an optical signal is transmitted bidirectionally in a single-core optical fiber.

  Therefore, although the configuration is complicated, various methods have been proposed as single-core bidirectional transmission optical amplifiers. For example, as shown in FIG. 17, conventional optical amplifiers 86 and 87 are used, and signals 252, 262, 272, and 282 traveling in different directions in the single-core bidirectional transmission lines 84 and 89 are converted into optical circulators 83 and 85. , 88, 90, and after being amplified separately in the vertical direction, the signals are multiplexed by the circulators 83, 85, 88, 90 again.

  At this time, the optical amplifiers 86 and 87 require an optical multiplexing element for multiplexing the pumping light and the signal light. Further, in order to separate the signals 252, 262, 272, and 282 in the single-core bidirectional transmission paths 84 and 89 vertically, an optical demultiplexing element is required. A technique has been proposed in which this optical multiplexing element and optical demultiplexing element are shared by a 4-port optical circulator (see, for example, Patent Document 1).

  Further, a configuration in which the optical multiplexing element and the optical demultiplexing element are shared by using a reflector when the excitation light and the signal light are combined in the optical amplifier (for example, see Patent Document 2), or A similar configuration has also been proposed (see, for example, Patent Document 3).

  On the other hand, as a technique for amplifying the optical signal in the vertical direction without separating it, an erbium-doped fiber is connected to the bidirectional transmission line, and the pumping light is applied in both the upper and lower directions to bidirectionally amplify the upstream and downstream optical signals. There is also a technique (see, for example, Patent Document 4).

JP-A-6-342950 (pages 4-6, FIG. 1) Japanese Patent Laid-Open No. 11-274625 (7th and 8th pages, FIG. 1) JP 2002-118313 A (5th and 6th pages, FIG. 1) JP-A-3-92828 (page 161, lower right column, page 162, upper left column, FIG. 6)

  Cost is a priority issue when targeting optical communication systems, particularly the metro area, and it is desirable to use low-cost products. Among the conventional single-core bidirectional optical amplifiers, as described in Patent Documents 1, 2, and 3, in the method of separating the optical signals in the vertical direction and amplifying each separately, the optical amplifier is 2 in the vertical direction. There is a problem that a stand is required, resulting in an increase in cost, an increase in device size, and an increase in power consumption.

  In this method, the separation of the upper and lower signals for bidirectional transmission and the multiplexing of the signal light and pumping light of the optical amplifier are combined to share the multiplexing / demultiplexing device. There is a problem that it is necessary to newly develop a dedicated one for the amplifier, which increases the cost.

  On the other hand, as a technique for amplifying an optical signal without separating the optical signal in the vertical direction, there is a technique described in Patent Document 4, but in an optical amplifier, at the junction or transmission line between the erbium-doped fiber and the transmission line, etc. It is essential to insert an optical isolator so that oscillation does not occur in the optical amplifier due to the reflection that occurs. Therefore, there is a problem that such a configuration cannot be realized.

  Further, the conventional single-core bidirectional optical amplifier assumes a transmission path that is symmetrical in the vertical direction, and amplifies the optical signal in the vertical direction equally. Therefore, an optical amplifier must be installed at the center of the single-core bidirectional transmission path, and there is a problem that installation conditions are limited.

  Further, when the transmission distance exceeds 60 km and the transmission speed per wavelength is 10 Gbps or more, not only optical amplification but also dispersion compensation is necessary, but there is a problem that this is not taken into consideration.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and to achieve a single-core bidirectional optical transmission system, a single-core bidirectional optical amplifier, and a single-core used for them that can achieve a long distance in a single-core bidirectional manner at low cost. To provide a bidirectional optical transmission method.

The single-core bidirectional optical transmission system according to the present invention multiplexes a plurality of optical signals of different wavelengths, and the first optical transmission / reception end and the second optical transmission / reception via the first and second single-core bidirectional transmission paths. A single-core bidirectional optical transmission system that performs bidirectional transmission with an end,
An optical amplifier is disposed between the first and second single-core bidirectional transmission lines ;
Between the optical amplifier and each of the first and second single-core bidirectional transmission lines, the wavelength division multiplexed light transmitted through the first and second single-core bidirectional transmission lines is separated for each direction. Including a directional separator
The optical amplifier includes: an optical amplifying unit; an optical multiplexing element and a first optical dispersion compensator placed on the input side; an optical demultiplexing element and a second optical dispersion compensator placed on the output side; Consists of
The first optical dispersion compensator is connected to the directional separator and the optical multiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The second optical dispersion compensator is connected to the direction separator and the optical demultiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second signals after being combined and amplified together. Is split into a signal to be output to the other of the one-core bidirectional transmission path .

A single-core bidirectional optical amplifier according to the present invention multiplexes optical signals of a plurality of different wavelengths, and a first optical transmission / reception end and a second optical transmission / reception end via first and second single-core bidirectional transmission paths. a single fiber bidirectional optical amplifier Ru using the single fiber bidirectional optical transmission system for bidirectional transmission to and from,
The optical amplifier includes an optical amplification unit, an optical multiplexing element and a first optical dispersion compensator placed on the input side, and an optical demultiplexing element and a second optical dispersion compensator placed on the output side. Become
The first optical dispersion compensator is connected to a direction separator connected to one of the first and second single-core bidirectional transmission lines and the optical multiplexing element,
The second optical dispersion compensator is connected to a direction separator connected to one of the first and second single-core bidirectional transmission lines and the optical demultiplexing element,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second optical signals. The signal is split into a signal to be output to the other of the two single-core bidirectional transmission paths .

A single-core bidirectional optical transmission method according to the present invention multiplexes a plurality of optical signals of different wavelengths, and a first optical transmission / reception end and a second optical transmission / reception via first and second single-core bidirectional transmission paths. A single-core bidirectional optical transmission method using a single-core bidirectional optical amplifier in a single-core bidirectional optical transmission system that performs bidirectional transmission with an end,
An optical amplifier is disposed between the first and second single-core bidirectional transmission lines;
Between the optical amplifier and each of the first and second single-core bidirectional transmission lines, the wavelength division multiplexed light transmitted through the first and second single-core bidirectional transmission lines is separated for each direction. Including a directional separator
The optical amplifier includes an optical amplifying unit, an optical multiplexing element and a first optical dispersion compensator placed on its input side, and an optical demultiplexing element and a second optical dispersion compensator placed on its output side. Become
The first optical dispersion compensator is connected to the directional separator and the optical multiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The second optical dispersion compensator is connected to the direction separator and the optical demultiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second signals after being combined and amplified together. Is split into a signal to be output to the other of the one-core bidirectional transmission path .

  That is, in the first single-core bidirectional optical transmission system of the present invention, in order to achieve the above object, a plurality of optical signals having different wavelengths are multiplexed and the first optical signal is transmitted via the single-core bidirectional transmission path. In a single-core bidirectional optical transmission system that performs bidirectional transmission between a transmission / reception end and a second optical transmission / reception end, bidirectional wavelength multiplexed optical signals are collectively amplified by a single optical amplifier.

  According to a second single-core bidirectional optical transmission system of the present invention, in the single-core bidirectional optical transmission system described above, an optical amplifier is provided only at the first optical transmission / reception end or the second optical transmission / reception end. Yes.

  In the third single-core bidirectional optical transmission system of the present invention, the wavelength division multiplexed light transmitted via the single-core bidirectional transmission path is a direction separator at the first optical transmission / reception end and the second optical transmission / reception end. It is characterized by separating for each direction.

  In the fourth single-core bidirectional optical transmission system of the present invention, the direction separator is any one of an optical circulator, a Blue / Red filter, and an optical interleaver.

  In the fifth single-core bidirectional optical transmission system of the present invention, the optical amplifier is placed on the output side of the optical amplifying unit, the optical multiplexing element and the first optical dispersion compensator placed on the input side thereof. The first optical dispersion compensator is connected to the optical transmitter and the optical multiplexing element at the first or second optical transmission / reception end provided with the optical amplifier. And the second optical dispersion compensator is connected to the optical receiver and the optical demultiplexing element at the first or second optical transmission / reception end provided with the optical amplifier, and is output from the optical transmitter and is subjected to the first dispersion compensation. The optical signal that has passed through the optical fiber and the optical signal that has propagated through the single-core bidirectional transmission path are combined and amplified together, and then both the signal that is output to the optical receiver via the second dispersion compensator and the single-core It is characterized by demultiplexing into an output signal in the direction transmission path.

  The sixth single-core bidirectional optical transmission system of the present invention is characterized in that the optical multiplexing element and the optical demultiplexing element are either a Blue / Red filter or an optical interleaver.

  In the seventh single-core bidirectional optical transmission system of the present invention, the optical amplifier in the single-core bidirectional optical transmission system is provided with an optical amplifying unit, an optical multiplexing element placed on the input side thereof, and an output side. Optical signal output from the optical transmitter at the first or second optical transmission / reception end provided with the optical amplifier, comprising the optical demultiplexing element, the optical dispersion compensator, and the optical direction separation element disposed at both ends thereof. And the optical signal propagating through the single-core bidirectional transmission line are combined, subjected to collective dispersion compensation and collective amplification, and then demultiplexed to match the optical receiver at the first or second optical transmission / reception end provided with the optical amplifier. It is characterized by outputting to a two-way bidirectional transmission line.

  The eighth single-core bidirectional optical transmission system of the present invention is characterized in that the optical multiplexing element and the optical demultiplexing element are either a Blue / Red filter or an optical interleaver.

  The ninth single-core bidirectional optical transmission system of the present invention is characterized in that the optical direction separation element is any one of an optical circulator, a Blue / Red filter, and an optical interleaver.

  The ninth single-core bidirectional optical transmission system of the present invention is characterized in that the above-described optical amplifier is arranged at the center of the transmission line.

  As described above, the present invention realizes a single-core bidirectional optical amplifier in which an optical amplifier is inserted into one end of a single-core bidirectional transmission line and a bidirectional optical signal is collectively amplified by one optical amplifier. Is.

  By adopting the above-described configuration and operation, the present invention provides an effect that it is possible to achieve a long distance in a single-core bidirectional manner at a low cost.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a single-core bidirectional optical transmission system according to a first embodiment of the present invention. In FIG. 1, one end of the transmission line (optical transmission / reception end A) includes a single-core bidirectional optical amplifier 1, a first optical transmitter (Tx) 2, and a first optical receiver (Rx) 3. Then, it is connected to the one-core bidirectional transmission path 5 through the optical circulator 4.

  The other end (optical transmission / reception end B) of the transmission path is composed of a second optical transmitter (Tx) 7 and a second optical receiver (Rx) 8, and passes through an optical circulator 6 with a single-core single mode fiber. It is connected to a single core bidirectional transmission path 5.

  The single-core bidirectional optical amplifier 1 includes an optical amplifying unit (for example, an erbium-doped fiber amplifying unit) 11, a Blue / Red filter 12 immediately before the optical amplifying unit 11, and a Blue / Red filter 13 immediately after the optical amplifying unit 11. Dispersion compensators (DCF) 14 and 15 are inserted between the Blue / Red filter 12 and the first optical transmitter 2 and between the Blue / Red filter 13 and the first optical receiver 3, respectively. Yes.

  FIG. 2 is a diagram showing the optical circulator 4 of FIG. In FIG. 2, an optical circulator 4 is an element that performs multiplexing / demultiplexing according to the direction of an optical signal. The insertion loss from the port 4a to the port 4b is 1 dB, and the isolation from the port 4a to the port 4c is 40 dB or more. Therefore, the light from the port 4a is transmitted only to the port 4b and does not travel to the port 4c.

  Similarly, the insertion loss from the port 4b to the port 4c is 1 dB, and the isolation from the port 4b to the port 4a is 40 dB or more. Therefore, the optical signal from the port 4b is transmitted only to the port 4c and does not proceed to the port 4a. In this way, bidirectional transmission is performed on the port 4b side, and unidirectional transmission is performed on the ports 4a and 4c side. Although not shown, the optical circulator 6 is the same as the optical circulator 4.

  3 is a diagram illustrating the Blue / Red filter 12 of FIG. 1, and FIG. 4 is a diagram illustrating characteristics of the Blue / Red filter. The Blue / Red filter 12 is an element that performs optical multiplexing / demultiplexing according to the wavelength band of the optical signal. Port 12a, port 12b, and port 12c are a Blue port, a Common port, and a Red port, respectively.

The transmission characteristics of the blue port 12a and the red port 12c are as shown in FIG. The insertion loss between the Blue port 12a and the Common port 12b, or the insertion loss between the Red port 12c and the Common port 12b are both 1 dB, and the isolation between the Blue port 12a and the Red port 12c is 30 dB or more.

  The passbands of the Blue port 12a and the Red port 12c are 1530.0 to 1543.2 nm and 1547.4 to 1561.0 nm, respectively. The Blue port 12a and the Red port 12c transmit only a signal having a wavelength within the passband, and the Common port 12b transmits regardless of the wavelength of the optical signal, so that multiplexing / demultiplexing is performed according to the wavelength band.

  Assuming that the optical signal from the first optical transmitter 2 has a transmission speed of 10 Gbps and the wavelength λ1 is 1558.98 nm, the optical signal from the second optical transmitter 7 has a transmission speed of 10 Gbps, and the wavelength λ2 is 1540.56 nm, the wavelength Since the optical signal of λ1 passes only through the Red port 12c and the optical signal of wavelength λ2 passes through only the Blue port 12a, the Blue / Red filter 12 performs multiplexing / demultiplexing depending on the wavelength. Although not shown, the Blue / Red filter 13 is the same as the Blue / Red filter 12.

  The optical amplifying unit 11 gives an equal gain to the optical signal of each channel of a WDM (Wavelength Division Multiplexing) signal with an input level of −30 to −15 dBm / ch and a wavelength range of 1535.1 to 1559.48 nm. When the level difference between the channels of the input signal is large and the power level is out of the range of −30 to −15 dBm, the gain level is reached and the output level becomes constant, and sufficient gain cannot be obtained. In some cases, variations in gain due to the channel may occur. Therefore, it is preferable that the level difference of the optical signal of each channel in the WDM signal is small.

  In the single-core bidirectional optical amplifier 1 according to this embodiment, the dispersion compensator 14 is inserted immediately after the first optical transmitter 2, so that the optical signal from the first optical transmitter 2 is sent to the optical amplifier 11. The difference between the input power level and the power level at which the optical signal from the second optical transmitter 7 is input to the optical amplifying unit 11 is made small.

  The optical signal output from the second optical transmitter 7 enters the optical amplifier 11 through the optical circulator 6, the single-core bidirectional transmission path 5, the optical circulator 4, and the Blue / Red filter 12. If the loss of the single core bidirectional transmission line 5 is 0.25 dB / km and the distance is 80 km, the optical signal output from the second transmitter 7 has a loss of 23 dB in total just before the incidence of the optical amplifying unit 11. receive.

  On the other hand, the optical signal output from the first optical transmitter 2 enters the optical amplifying unit 11 through the dispersion compensator 14 and the Blue / Red filter 12. At this time, assuming that the dispersion compensation amount is −1360 ps / nm, which is dispersion at 80 km transmission, and the loss is 10 dB, the loss of the optical signal output from the first transmitter 2 immediately before the incidence of the optical amplifying unit 11 is received. The total is 11 dB.

  As a result, when the output of the first optical transmitter 2 and the output of the second optical transmitter 7 are both -5 dBm, the power level of the optical signal when the optical signal enters the optical amplifying unit 11 is -16 dBm, respectively. And -28 dBm, and the power level difference is 12 dB, which is a range in which a sufficient gain in both directions can be secured.

  If the gain of the optical amplifying unit 11 is 25 dB, the power at the first optical receiver 3 and the second optical receiver 8 is −14 dBm, and −18 dBm, which is the reception sensitivity of the 10 Gbps optical IF (interface). Because it exceeds, there is no problem.

  Furthermore, the input from the optical circulator 4 to the single-core bidirectional transmission line 5 is 7 dBm, and there is no problem with the influence of the nonlinear optical effect. As described above, single fiber bidirectional transmission of 10 Gbps and 80 km can be realized using the single fiber bidirectional optical amplifier 1 according to the first embodiment of the present invention.

  FIG. 5 is a block diagram showing a configuration of a single-core bidirectional optical transmission system according to the second embodiment of the present invention. In FIG. 5, the single-core bidirectional optical transmission system according to the second embodiment of the present invention has a configuration in which the optical circulators 4 and 6 are replaced with blue / red filters 16 and 17 to multiplex / demultiplex optical signals in the vertical direction. Except for this, the configuration is the same as that of the first embodiment of the present invention shown in FIG. The operation of the same component is the same as that of the first embodiment of the present invention.

  The Blue / Red filters 16 and 17 are passbands having the same wavelength as that of the Blue / Red filters 12 and 13. As a result, in the second embodiment of the present invention, similarly to the first embodiment of the present invention described above, single-core bidirectional transmission of 10 Gbps and 80 km can be realized using the single-core bidirectional amplifier 1. it can.

  FIG. 6 is a block diagram showing the configuration of a single-core bidirectional optical transmission system according to the third embodiment of the present invention. In FIG. 6, the single-core bidirectional optical transmission system according to the third embodiment of the present invention has a configuration in which the optical circulators 4 and 6 are replaced with optical interleavers 18 and 19 to multiplex and demultiplex optical signals in the vertical direction. The configuration is the same as that of the first embodiment of the present invention shown in FIG. The operation of the same component is the same as that of the first embodiment of the present invention.

  FIG. 7 is a diagram showing the optical interleaver 18 of FIG. In FIG. 7, a multiplexed signal with a wavelength interval of 100 GHz in the port 18b is demultiplexed into an even channel and an odd channel with a wavelength interval of 200 GHz with respect to the port 18a and the port 18c via the optical interleaver 18.

  Conversely, the multiplexed signals at intervals of 200 GHz input from the ports 18a and 18c are multiplexed into the multiplexed signals at intervals of 100 GHz at the port 18b via the optical interleaver 18. Since the wavelengths λ1 = 1558.98 and λ2 = 154.56 are 192.30 THz and 194.60 THz, respectively, λ1 passes through the port 18a of the optical interleaver 18 and λ2 passes through the port 18b of the optical interleaver, respectively.

  Since the loss of the optical interleaver 18 is 1 dB, the optical signal powers of the wavelengths λ1 and λ2 input to the optical amplifying unit 11 are −16 dB and −28 dB, and similarly to the above-described first embodiment of the present invention, the optical amplifying unit. 11 is a range which operates linearly. Thus, in this embodiment, the single fiber bidirectional optical amplifier 1 can be used to realize the single fiber bidirectional transmission of 10 Gbps and 80 km. Although not shown, the optical interleaver 19 is the same as the optical interleaver 18.

  FIG. 8 is a block diagram showing the configuration of a single-core bidirectional optical transmission system according to the fourth embodiment of the present invention. 8, the single-core bidirectional optical transmission system according to the fourth embodiment of the present invention is the same as that shown in FIG. 1 except that the blue / red filters 12 and 13 are replaced with optical interleavers 21 and 22 to perform multiplexing / demultiplexing. The configuration is the same as that of the first embodiment of the present invention. The operation of the same component is the same as that of the first embodiment of the present invention.

  The optical interleavers 21 and 22 have the same characteristics as the optical interleavers 18 and 19 in the third embodiment of the present invention described above. As a result, in this embodiment, similarly to the first embodiment of the present invention described above, the single-core bidirectional amplifier 20 can be used to realize the single-core bidirectional transmission of 10 Gbps and 80 km.

  At this time, this embodiment can also be realized by replacing the optical circulators 21 and 22 with a Blue / Red filter, as in the second embodiment of the present invention described above. In this embodiment, the optical circulators 4 and 6 can be realized as an optical interleaver as in the above-described third embodiment of the present invention.

  FIG. 9 is a block diagram showing the configuration of a single-core bidirectional optical transmission system according to the fifth embodiment of the present invention. In FIG. 9, the single-core bidirectional optical transmission system according to the fifth embodiment of the present invention performs multiplexing and demultiplexing using a plurality of channels of optical multiplexing elements 36 and 45 and optical demultiplexing elements 35 and 46. It is configured to perform unidirectional multiplex channel WDM transmission.

  In this embodiment, two waves / direction, a total of 2 × 2 wavelengths, is transmitted. The wavelengths of the optical signals from the optical transmitters 31, 32, 41, and 42 are λ11 = 1558.98 nm, λ12 = 1557.36 nm, λ13 = 1540.56 nm, and λ14 = 1538.98 nm, respectively, and the optical output power is − 1 dBm.

  FIG. 10 is a diagram showing the characteristics and wavelength arrangement of the Blue / Red filter, and FIG. 11 is a diagram showing the configuration and wavelength arrangement of the optical interleaver. FIG. 10 shows the relationship between the wavelength arrangement of the signal lights λ11 to λ14 and the bands of the Blue / Red filters 12 and 13.

  The passband bandwidths of the Blue band and the Red band are the same as the bands shown in the first embodiment of the present invention described above. Since the optical signals of wavelengths λ11 and λ12 pass only through the Red band and the optical signals of wavelengths λ13 and λ14 pass through only the Blue band, the optical signals of wavelengths λ11 and λ12 and wavelengths λ13 and λ14 are multiplexed / demultiplexed according to the wavelength. The

  If the optical multiplexing elements 36 and 45 and the optical demultiplexing elements 35 and 46 have a loss of 3 dB, the single-core bidirectional transmission path 5 has 80 km and a loss of 20 dB, the power input to the optical amplifying unit 11 has wavelengths λ11 and λ12. Since the -15 dBm per channel and the wavelengths λ13 and λ14 are −27 dBm per channel and the power level difference of the input optical signal is 12 dB, the optical amplifier 11 operates linearly as in the first embodiment of the present invention described above. It is a range.

  Since the gain is 25 dB, the optical power at the optical receivers 33, 34, 43, and 44 is -16 dBm, which is a receivable level. As a result, in this embodiment, it is possible to achieve 10 Gbps and 80 km 4-channel single-core bidirectional transmission using the single-core bidirectional optical amplifier 30.

  At this time, in this embodiment, as in the second embodiment of the present invention described above, the optical circulators 4 and 6 can use Blue / Red filters in the same band as the Blue / Red filters 12 and 13.

  Further, the frequencies of the signals from the wavelength λ11 to the wavelength λ14 are 192.30 THz, 192.50 THz, 194.60 THz, and 194.40 THz, respectively, and the frequency arrangement of the signal light λ11 to λ14 is shown in FIG. Since the wavelengths λ11 and λ12 and the wavelengths λ13 and λ14 are separated into separate ports by the interleaver 37, the optical circulators 4 and 6 can be realized by an optical interleaver as in the third embodiment of the present invention described above. It is. Furthermore, in this embodiment, the Blue / Red filters 12 and 13 in the single-core bidirectional optical amplifier 30 may be optical interleavers, as in the fourth embodiment of the present invention described above.

  FIG. 12 is a block diagram showing the configuration of a single-core bidirectional optical transmission system according to the sixth embodiment of the present invention. In FIG. 12, in the single-core bidirectional optical transmission system according to the sixth embodiment of the present invention, optical circulators 51 and 52 are installed before and after the dispersion compensator 15, and optical signals in the vertical direction are sent before and after the dispersion compensator 15. The two dispersion compensators 14 and 15 used in the first to fifth embodiments of the present invention described above are combined into one by combining and demultiplexing and performing bidirectional collective dispersion compensation on the dispersion compensating fiber. A single-core bidirectional optical amplifier 50 is constituted by the single dispersion compensator 15.

  The output wavelengths of the first optical transmitter 2 and the second optical transmitter 7 are λ1 = 1558.98 nm and λ2 = 1540.56 nm, as in the first embodiment of the present invention described above. The dispersion compensation amount of the dispersion compensator 15 is −1360 ps / nm and the loss is 10 dB, as in the first embodiment of the present invention described above.

  Assuming that the outputs of the first optical transmitter 2 and the second optical transmitter 7 are −5 dBm, the optical powers of the wavelengths λ 1 and λ 2 input to the optical amplifier 11 are −18 dBm and −28 dBm, respectively. As in the first embodiment, the optical amplifying unit 11 is in a range that operates linearly. The power at the first optical receiver 3 and the second optical receiver 8 is −16 dBm, which is a receivable level. Thus, in this embodiment, the single fiber bidirectional optical amplifier 50 can be used to realize the single fiber bidirectional transmission of 10 Gbps and 80 km.

  Here again, the optical circulators 4, 6, 51, 52 are provided with a Blue / Red filter or an optical interleaver in the same band as the Blue / Red filters 12, 13, as in the second and third embodiments of the present invention described above. Can be used.

  Further, in this embodiment, the Blue / Red filters 12 and 13 in the single-core bidirectional optical amplifier 50 may be optical interleavers as in the above-described fourth embodiment of the present invention. Further, in the present embodiment, as in the fifth embodiment of the present invention described above, unidirectional multi-channel WDM transmission can be performed using an optical multiplexing element and an optical demultiplexing element.

  FIG. 13 is a block diagram showing a configuration of a single-core bidirectional optical transmission system according to the seventh embodiment of the present invention. In FIG. 13, the single-core bidirectional optical transmission system according to the seventh embodiment of the present invention has a configuration in which the single-core bidirectional optical amplifier 1 is inserted in the middle of the transmission line.

  By installing the optical circulators 4, 61, 62 before and after the single-core bidirectional optical amplifier 1, not only the end stations of the transmission line in the first to sixth embodiments of the present invention but also the middle of the transmission line. Can be inserted into.

  The output wavelengths of the first optical transmitter 2 and the second optical transmitter 7 are λ1 = 1558.98 nm and λ2 = 1540.56 nm, as in the first embodiment of the present invention described above. The dispersion compensation amounts of the dispersion compensators 14 and 15 are −1360 ps / nm and the loss is 10 dB, as in the first embodiment of the present invention described above.

  In this embodiment, the distances from the single-core bidirectional optical amplifier 1 to the optical transmission / reception end A and the optical transmission / reception end B are 20 km and 60 km, respectively, and the losses of the single-core bidirectional transmission lines 5 and 63 at this time are 5 dB and 15 dB, respectively. And

  Assuming that the outputs of the first optical transmitter 2 and the second optical transmitter 7 are −5 dBm, the optical signal powers of the wavelengths λ1 and λ2 input to the optical amplifying unit 11 are −23 dBm and −23 dBm, respectively. Similar to the first embodiment of the invention, this is the range in which the optical amplifying unit 11 operates linearly. The optical power at the first optical receiver 3 and the second optical receiver 8 is −16 dBm, which is a receivable level. As a result, in this embodiment, it is possible to realize 10-Gbps, 80-km single-core bidirectional transmission without limiting the installation location of the single-core bidirectional optical amplifier 1 to the center of the transmission line.

  At this time, in this embodiment, a Blue / Red filter or an optical interleaver can be used in place of the optical circulators 4, 6, 61, 62 as in the second and third embodiments of the present invention described above. is there.

  Further, in this embodiment, the Blue / Red filters 12 and 13 in the single-core bidirectional optical amplifier 1 may be optical interleavers as in the above-described fourth embodiment of the present invention. Further, in the present embodiment, as in the fifth embodiment of the present invention described above, unidirectional multi-channel WDM transmission can be performed using an optical multiplexing element and an optical demultiplexing element.

  FIG. 14 is a block diagram showing the configuration of a single-core bidirectional optical transmission system according to the eighth embodiment of the present invention. In FIG. 14, the single-core bidirectional optical transmission system according to the eighth embodiment of the present invention includes a single-core bidirectional optical amplifier 70 comprising an optical amplifying unit 11 and blue / red filters 12 and 13 placed before and after the optical amplifier. Since the transmission distance is short, the dispersion compensator is not used.

  In this embodiment, the transmission distance is 60 km, the loss is 15 dB, and bidirectional transmission of 4 waves / direction, a total of 4 × 2 wavelengths is performed. A low-cost coupler is used for the optical multiplexing element 74, the loss is 9 dB, and the losses of the optical multiplexing element 77 and the optical demultiplexing elements 73 and 78 are 5 dB.

  The wavelengths of the optical signals from the respective optical transmitters 71-1 to 71-4 and 75-1 to 75-4 are λ21 = 1558.98 nm, λ22 = 1555.36 nm, λ23 = 1555.75 nm, λ24 = 1554.13, λ25 = 1540.56 nm, λ26 = 1538.98 nm, λ27 = 1537.40, λ28 = 1535.82, and the optical output power is −5 dBm.

  FIG. 15 is a diagram showing the characteristics and wavelength arrangement of the Blue / Red filter, and FIG. 16 is a diagram showing the configuration and wavelength arrangement of the optical interleaver. FIG. 15 shows the relationship between the wavelength arrangement of the signal lights λ21 to λ28 and the bands of the Blue / Red filters 12 and 13.

  The passband bandwidths of the Blue band and the Red band are the same as the bands shown in the first embodiment of the present invention described above. Since the optical signals of wavelengths λ21 to λ24 pass only through the Red band and the optical signals of wavelengths λ25 to λ28 pass through only the Blue band, the optical signals of wavelengths λ21 to λ24 and wavelengths λ25 to λ28 are multiplexed / demultiplexed according to the wavelength. The

  The powers of the wavelengths λ21 to 24 and λ25 to 28 input to the optical amplifying unit 11 are −15 and −28 dBm per channel, respectively, and the power level difference from the input signal is 13 dB. Therefore, the first embodiment of the present invention described above is used. Similarly, the optical amplification unit 11 is in a range in which it operates linearly.

  Since the gain is 25 dB, the optical powers in the optical receivers 72-1 to 72-4 and 76-1 to 76-4 are -8 dBm and -13 dBm, which are receivable levels. Thus, in this embodiment, 8-channel single-core bidirectional transmission of 10 Gbps and 60 km can be realized using the single-core bidirectional optical amplifier 70.

  At this time, in this embodiment, the optical circulators 4 and 6 may be Blue / Red filters in the same band as the Blue / Red filters 12 and 13 as in the second embodiment of the present invention described above.

  In this embodiment, the frequency of each signal from the wavelength λ21 to the wavelength λ28 is 192.30 THz, 192.50 THz, 192.70 THz, 192.90 z, 194.60 THz, 194.80 THz, 195.00 THz, 195. 20 THz, and the wavelengths λ21 to λ24 and λ25 to λ28 are divided into separate ports by the optical interleaver 79 shown in FIG. 16 in the frequency arrangement of the signal light λ21 to λ28, so that the Blue / Red filters 12, 13 and the optical circulator 4 , 6 can also be realized by an optical interleaver, as in the third embodiment of the present invention described above. Further, as in the fourth embodiment of the present invention described above, the Blue / Red filters 12 and 13 in the single-core bidirectional optical amplifier 70 may be optical interleavers.

  In the above description, the optical amplifying unit 11 is an erbium-doped fiber amplifying unit, but this may be an optical amplifying unit or a semiconductor optical amplifying unit using a fiber added with other rare earths depending on the wavelength of the optical signal to be amplified. .

  The Blue / Red filter is also a C-band Blue / Red filter, but may be a filter used in another band depending on the wavelength range used.

  Furthermore, in the configuration of the present invention, an element depending on the transmission rate is not used, and the transmission rate may be, for example, 2.4 Gbps or 10 Gbps. Thus, in the above configuration, as long as the above-described functions are satisfied, the optical signal wavelength, the transmission speed, and the transmission distance are free, and the above description does not limit the present invention.

  Thus, the single-core bidirectional optical amplifier according to the present invention can be realized at low cost, and in the single-core bidirectional transmission path 5 that transmits bidirectionally on a single-core fiber, at either end of the transmission path. Since only the optical amplifier 11 is inserted and a single optical amplifier 11 can amplify optical signals in both the upper and lower directions at a time, it is possible to increase the distance in a single-core bidirectional manner at a low cost. Further, the single-core bidirectional optical amplifier of the present invention can be realized at a low cost because it can be realized with a simple configuration in which passive components are added to a normal optical amplifier.

1 is a block diagram illustrating a configuration of a single-core bidirectional optical transmission system according to a first embodiment of the present invention. It is a figure which shows the optical circulator of FIG. It is a figure which shows the Blue / Red filter of FIG. It is a figure which shows the characteristic of a Blue / Red filter. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 2nd Example of this invention. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 3rd Example of this invention. It is a figure which shows the optical interleaver of FIG. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 4th Example of this invention. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 5th Example of this invention. It is a figure which shows the characteristic and wavelength arrangement | positioning of a Blue / Red filter. It is a figure which shows the structure and wavelength arrangement | positioning of an optical interleaver. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 6th Example of this invention. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 7th Example of this invention. It is a block diagram which shows the structure of the single core bidirectional | two-way optical transmission system by the 8th Example of this invention. It is a figure which shows the characteristic and wavelength arrangement | positioning of a Blue / Red filter. It is a figure which shows the structure and wavelength arrangement | positioning of an optical interleaver. It is a figure which shows the conventional single core bidirectional | two-way optical transmission system.

Explanation of symbols

1,20,
30, 50, 70 Single-core bidirectional optical amplifier
2 First optical transmitter
3 First optical receiver 4, 6, 51, 52,
61, 62 Optical circulators 4a-4c,
12a-12c,
18a-18c,
37a-37c port
5,63 single-core bidirectional transmission line
7 Second optical transmitter
8 Second optical receiver
11 Optical Amplifier 12, 13, 16, 17 Blue / Red Filter
14, 15 Dispersion compensator 18, 19,
21, 22, 37, 79 Optical interleavers 31, 32, 41, 42,
71-1 to 71-4,
75-1 to 75-4 optical transmitters 33, 34, 43, 44,
72-1 to 72-4,
76-1 to 76-4 Optical receiver 36, 45, 74, 77 Optical multiplexing element 35, 36, 73, 78 Optical demultiplexing element
A, B Optical transceiver

Claims (9)

A single core that multiplexes optical signals of different wavelengths and performs bidirectional transmission between the first optical transmission / reception end and the second optical transmission / reception end via the first and second single-core bidirectional transmission paths. A bidirectional optical transmission system,
An optical amplifier is disposed between the first and second single-core bidirectional transmission lines ;
Between the optical amplifier and each of the first and second single-core bidirectional transmission lines, the wavelength division multiplexed light transmitted through the first and second single-core bidirectional transmission lines is separated for each direction. Including a directional separator
The optical amplifier includes: an optical amplifying unit; an optical multiplexing element and a first optical dispersion compensator placed on the input side; an optical demultiplexing element and a second optical dispersion compensator placed on the output side; Consists of
The first optical dispersion compensator is connected to the directional separator and the optical multiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The second optical dispersion compensator is connected to the direction separator and the optical demultiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second signals after being combined and amplified together. A single-core bidirectional optical transmission system, wherein the signal is split into a signal output to the other of the single-core bidirectional transmission path . 2. The single-core bidirectional optical transmission system according to claim 1 , wherein the direction separator is at least one of an optical circulator, a Blue / Red filter, and an optical interleaver . 3. The single-core bidirectional optical transmission system according to claim 1, wherein the optical multiplexing element and the optical demultiplexing element are at least one of a Blue / Red filter and an optical interleaver . A single core that multiplexes optical signals of different wavelengths and performs bidirectional transmission between the first optical transmission / reception end and the second optical transmission / reception end via the first and second single-core bidirectional transmission paths. A single-core bidirectional optical amplifier for use in a bidirectional optical transmission system,
The optical amplifier includes an optical amplification unit, an optical multiplexing element and a first optical dispersion compensator placed on the input side, and an optical demultiplexing element and a second optical dispersion compensator placed on the output side. Become
The first optical dispersion compensator is connected to a direction separator connected to one of the first and second single-core bidirectional transmission lines and the optical multiplexing element,
The second optical dispersion compensator is connected to a direction separator connected to one of the first and second single-core bidirectional transmission lines and the optical demultiplexing element,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second optical signals. A single-core bidirectional optical amplifier, which demultiplexes a signal output to the other of two single-core bidirectional transmission paths. 5. The single-core bidirectional optical amplifier according to claim 4, wherein the direction separator is at least one of an optical circulator, a Blue / Red filter, and an optical interleaver. 6. The single-core bidirectional optical amplifier according to claim 4, wherein the optical multiplexing element and the optical demultiplexing element are at least one of a Blue / Red filter and an optical interleaver. A single core that multiplexes optical signals of different wavelengths and performs bidirectional transmission between the first optical transmission / reception end and the second optical transmission / reception end via the first and second single-core bidirectional transmission paths. A single-core bidirectional optical transmission method using a single-core bidirectional optical amplifier in a bidirectional optical transmission system,
An optical amplifier is disposed between the first and second single-core bidirectional transmission lines;
Between the optical amplifier and each of the first and second single-core bidirectional transmission lines, the wavelength division multiplexed light transmitted through the first and second single-core bidirectional transmission lines is separated for each direction. Including a directional separator
The optical amplifier includes an optical amplifying unit, an optical multiplexing element and a first optical dispersion compensator placed on its input side, and an optical demultiplexing element and a second optical dispersion compensator placed on its output side. Become
The first optical dispersion compensator is connected to the directional separator and the optical multiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The second optical dispersion compensator is connected to the direction separator and the optical demultiplexing element connected to one of the first and second single-core bidirectional transmission lines,
The optical signal output from one of the first and second single-core bidirectional transmission lines and propagates through the first dispersion compensator and the other of the first and second single-core bidirectional transmission lines. And a signal to be output to one of the first and second single-core bidirectional transmission lines via the second dispersion compensator and the first and second signals after being combined and amplified together. A single-core bidirectional optical transmission method, comprising: demultiplexing a signal output to the other of the single-core bidirectional transmission path. The single-core bidirectional optical transmission method according to claim 7, wherein the direction separator is at least one of an optical circulator, a Blue / Red filter, and an optical interleaver. 9. The single-core bidirectional optical transmission method according to claim 7, wherein the optical multiplexing element and the optical demultiplexing element are at least one of a Blue / Red filter and an optical interleaver.

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