JP2006180417A - Optical transmission equipment - Google Patents

Abstract

【Task】
In a network node that combines an optical add / drop device and an optical space transmission device, if a failure occurs in the optical space transmission path, power level fluctuations of wavelength multiplexed signals other than the wavelength assigned for branching / insertion occur. Repress.
[Solution]
According to the present invention, the signal light branched from the wavelength multiplexed signal by the optical branching means in the optical add / drop apparatus is transmitted to the external space, and the signal light received from the outside is transmitted to the optical add / drop means in the optical add / drop apparatus. In an optical transmission device that is inserted into a wavelength multiplexed signal by
An optical amplifier is provided to keep the power level of the signal received from the outside constant. When the signal light from the outside is in a signal interruption state, the signal light branched from the wavelength multiplexed signal by the optical branching means is provided. Provided is an optical transmission device provided with a loopback optical switch for loopback and insertion into a wavelength multiplexed signal by an optical insertion means.
[Selection] Figure 1

Description

  The present invention relates to an optical transmission device such as an optical add-drop device and an optical space transmission device, and in particular, a technique for suppressing the influence in the optical add-drop device when a signal failure occurs on the optical space transmission device side. The present invention relates to an optical transmission device.

  An optical space (optical wireless) transmission device is an optical communication device that uses a free space as a transmission path, and does not require authorization or construction associated with fiber laying. As a result, a service application is made to the optical fiber transmission device. There is an advantage that the period from the start of service to the start of service can be greatly shortened, and an advantage that construction costs can be reduced (for example, see Non-Patent Document 1).

  A general configuration of an optical space transmission apparatus is shown in FIG. FIG. 2 shows a configuration in which two optical space transmission devices 1 and 2 are opposed to each other with the space transmission path 3 interposed therebetween. The electrical signal input to the optical space transmission device 1 is converted into signal light by the optical wireless transmitter 4a, and is transmitted to the space from the transmission optical system 5a. In the optical space transmission device 2, the signal light transmitted from the optical space transmission device 1 is received by the reception optical system 6a, converted into an electrical signal by the optical wireless receiver 7a, and output. The optical wireless transmitter 4a and the transmission optical system 5a are connected by a spatial optical system or an optical fiber, and the transmission optical system 5a functions to form a beam shape suitable for long-distance communication with the signal light from the optical wireless transmitter 4a. . Similarly, the reception optical system 6a and the optical wireless receiver 7a are connected by a spatial optical system or an optical fiber, and the reception optical system 6a collects the received signal light beam and inputs it to the light receiving wireless receiver 7a. I do. Similarly, in the communication from the optical space transmission device 2 to the optical space transmission device 1, the signal propagates in the order of the optical wireless transmitter 4b, the transmission optical system 5b, the spatial transmission path 3, the reception optical system 6b, and the optical wireless receiver 7c. Realizes two-way communication.

  An optical add drop multiplexer (OADM) is a device that branches (drops) or inserts (adds) part of a wavelength-multiplexed signal, and converts the signal light into an electrical signal. Rather, it is an apparatus that makes it possible to access only a desired wavelength among a plurality of wavelengths that are wavelength-multiplexed without changing the signal light. By using this optical add / drop device at each node on the optical network, it becomes possible to handle only the desired wavelength instead of handling all wavelength-multiplexed signals. Reduction and efficient signal wavelength allocation.

  FIG. 3 shows a general configuration of the optical add / drop device. FIG. 3 shows an optical add / drop device that assumes a wavelength multiplexed signal in which four wavelengths (λ1, λ2, λ3, λ4) are multiplexed. The wavelength multiplexed signals input to the optical add / drop device 11 are collectively amplified by the optical amplifier 18, then demultiplexed into the respective wavelengths λ 1, λ 2, λ 3, and λ 4 by the demultiplexer 12 and input to separate fibers. . The signal of λ1 is input to the optical branch switch 13, and depending on the state of the optical branch switch 13, the signal of λ1 passes through the optical branch switch 13 as it is and reaches the optical add switch 14, or the signal of λ1 branches (Dropped) and output from the optical branch switch 13 to the outside of the optical add / drop device 11. The optical add switch 14 outputs either the signal light λ1 that has been passed (through) or the signal light λ1 'that has been input (inserted) from the outside of the optical add / drop device 11. The signal light λ 1 or λ 1 ′ output from the optical insertion switch 14 is combined with signals λ 2, λ 3, λ 4 of other wavelengths by the optical multiplexer 15 to form a wavelength multiplexed signal again, and is collectively amplified by the optical amplifier 19 Is output from the optical add / drop device 11.

  In the optical add / drop apparatus, the optical amplifier 18 and the optical amplifier 19 are not necessarily installed, but are often installed in order to compensate for the loss of the optical demultiplexer 12 and the optical multiplexer 15. In the configuration of FIG. 3, only the wavelength of λ1 is branched and inserted by the optical branching switch 13 and the optical insertion switch 14, but can be installed at any other wavelength, and the optical branching switch 13 Or only one of the optical insertion switches 14 may be installed. In addition, when there is no need to change the network configuration, a patch cord connection may be substituted for the optical branch switch 13 and the optical add switch 14 without providing a switch. The detailed configuration of these optical add / drop apparatuses is designed in consideration of the network scale, the presence / absence of changes, apparatus costs, and the like, and can take various forms.

  An example of a network configuration using such an optical add / drop device is shown in FIG. FIG. 4 shows an example in which communication between the node A and the node B is realized by adding / dropping λ1 of the wavelength-multiplexed signals at the node A (21) and the node B (22), respectively. The optical branch switches 13a and 13d are both set on the branch side, and the optical add switches 14b and 14c are both set on the insert side. Further, the description of the optical amplifier installed immediately before the optical demultiplexer 12 and the optical amplifier installed immediately after the optical multiplexer 15 is omitted in FIG.

  As network configurations, lines (fibers 23e, 23c, 23a) from the node B (22) to the node A (21) and lines (fibers 23b, 22d, 23f) from the node A (21) to the node B (22) Therefore, the optical add / drop apparatus shown in FIG. 3 is installed in both the node A (21) and the node B (22).

  The signal light λ1 output from the optical transmitter 16c of the node B (22) passes through the optical insertion switch 14c and the optical multiplexer 15c, is output as a wavelength multiplexed signal, and enters the optical fiber 23c. The wavelength multiplexed signal reaching the node A (21) is demultiplexed by the optical demultiplexer 12a. Among these, the signal light λ1 reaches the optical receiver 17a through the optical branching switch 13a. Thus, communication using λ1 is established from the node B (22) to the node (21). Similarly, communication using λ1 from the node A (21) to the node B (22) is performed using the optical transmitter 16b, the optical add switch 14b, the optical multiplexer 15b, the optical fiber 23b, the optical demultiplexer 12d, and the optical branching switch. 13d, which is established along the path of the optical receiver 17d. In this way, in the node A (21) and the node B (22) where the optical add / drop apparatus is installed, it is not necessary to install four optical transceivers corresponding to each of the wavelength multiplexed four wavelengths. It is possible to handle a desired signal by installing only one optical transceiver 16b, 17a, 16c, and 17d for each (λ1).

  In recent years, with the spread of the Internet and multimedia services, the demand for optical communication has expanded not only to the conventional backbone network and the metro network but also to the access network to the subscriber site. Under these circumstances, in order to meet the need for flexible and low-cost access to the wavelength division multiplexing line on the subscriber side, a part of the wavelength division multiplexed signal can be obtained by fusing the optical space transmission device and the optical add / drop device. It is possible to consider an operation mode in which optical space transmission is performed.

  FIG. 5 shows an example in which an optical space transmission device and an optical add / drop device are combined. FIG. 5 can also be said to be a form in which the optical space radio apparatus of FIG. 1 is directly connected to the node A of the network of FIG. The signal light λ1 branched from the optical branching switch 13a at the node A (24) reaches the optical receiver 17a. The output electrical signal from the optical receiver 17a is converted into signal light by the optical wireless transmitter 4a of the optical space transmission device, and sent to the spatial transmission path 3 through the transmission optical system 5a. In the node C (25), the optical space signal from the node A (24) is received by the reception optical system 6a, converted into an electric signal by the optical wireless receiver 7a, and output.

  Similarly, from the node C (25) to the node A (24), the optical wireless transmitter 4b, the transmission optical system 5b, the spatial transmission path 3, the reception optical system 6b, the optical wireless receiver 7b, and the optical transmitter 16b. After passing through the optical add switch 14b and the optical multiplexer 15b, the signal from the node C is converted into λ1 and then inserted into the wavelength multiplexed signal.

JP 2000-201111 A JP 2002-185407 A JP 2000-174701 A “Research on Outdoor Optical Wireless Propagation Characteristics (1) to (5)”, Matsumoto, Kakishima, Suzuki, Narui, Hattori, Miyamoto, 2003 IEICE Communication Society Conference, Paper No. B5-137-141, p. . 514-518

  However, in the form of FIG. 5, the node A (24) converts the signal of λ1 into electricity and then sends it to the node C as it is, and the node C (25) needs all the information in the signal of λ1. Even if not, an excessive number of four transmitters / receivers, that is, the optical transmitter 16b, the optical receiver 17a, the optical wireless transmitter 4a, and the optical wireless receiver 7b, are excessively required, resulting in an increase in complexity and cost of the device. End up.

  Such excessive installation of transceivers can be improved by using the signal of λ1 as it is for spatial transmission as in the system of the form shown in FIG. In the system shown in FIG. 6, the signal light λ1 branched by the optical demultiplexer 12a and the optical branching switch 13a is not converted into an electric signal, but is sent as it is from the transmission optical system 5a to the spatial transmission path 3. In the node C (27), the signal λ1 from the node A (26) is received by the receiving optical system 6a and the optical wireless receiver 7a and converted into an electric signal.

  Further, a signal of wavelength λ1 is output from the optical wireless transmitter 4b from the node C (27), and is transmitted to the spatial transmission path 3 through the transmission optical system 5b. In the node A (26), the signal λ1 from the node C (27) is received by the receiving optical system 6b, and without being converted into an electrical signal, it is converted into a wavelength multiplexed signal through the optical add switch 14b and the optical multiplexer 15b. Inserted. In this way, it is possible to form a more flexible and low-cost network by applying the optical signal to the optical space transmission as it is without once converting the branched and inserted signal light into an electrical signal.

  Here, in optical space transmission, the transmission characteristics are very susceptible to weather conditions, and particularly large attenuation occurs due to rain, fog, dust, etc., so care must be taken in operating the apparatus and system. This is because when the propagation loss increases due to weather conditions such as rain, fog, dust, etc., the received light level is remarkably lowered, or in the worst case, the signal cannot be received. As in the system of FIG. 6, in a system in which signal light that has been added and dropped is directly applied to optical space transmission, the deterioration of the optical space transmission path due to the deterioration of the weather conditions described above is caused by the signal (λ1) for optical space transmission. In addition, the quality of other wavelength-multiplexed signals (λ2, λ3, λ4) may be deteriorated. This phenomenon will be described below.

  In the system shown in FIG. 6, node A (26) and node C (27) are connected via a spatial transmission line (3). Here, when the loss of the spatial transmission path increases due to deterioration of weather conditions such as rain, fog, and dust, the reception power in the reception optical system 6a and the reception optical system 6b decreases. Of these, the signal λ1 received on the receiving optical system 6b side passes through the optical add switch 14b and the optical multiplexer 15b as they are, and is combined with other signals (λ2, λ3, λ4) to form a wavelength multiplexed signal. In general, the optical add / drop apparatus designs the loss of each element so that the power level of each wavelength of the wavelength multiplexed signal to be output is substantially equal. However, since the power level of the signal λ1 has decreased due to the deterioration of weather conditions, the power level of λ1 is lower than the other signals (λ2, λ3, λ4) at the output of the optical multiplexer 15b.

  As described above, the optical add / drop device is provided with optical amplifiers (18a, 18b, 19a, 19b) in order to compensate for the loss of the switches and multiplexers / demultiplexers. The optical amplifier usually has some output control mechanism for stable operation, and the total optical output power at the optical amplifier (in the case of wavelength multiplexed signal light, the power for all wavelengths) is always constant. In many cases, a constant total output control mechanism is applied.

  Consider a case where the power level of the signal light λ1 is reduced due to weather fluctuations as described above in the input wavelength multiplexed signals (λ1, λ2, λ3, λ4) of the optical amplifier 19b subjected to the total output constant control. At this time, the power level of each signal light (λ1, λ2, λ3, λ4) at the input and output of the optical amplifier 19b is shown in FIG. Prior to the occurrence of power level fluctuations due to weather fluctuations (state 1), the input power of the optical amplifier 19b is the same for all signals. Even when the power level fluctuates and the signal light λ1 decreases (state 2), the input power of the other signal light (λ2, λ3, λ4) remains constant.

  However, when looking at the output power of the optical amplifier 19b, since the optical amplifier 19b is subjected to the total output constant control, the gain of the optical amplifier 19b increases to compensate for the decrease of the signal light λ1, and as a result, As a result, other signal lights (λ2, λ3, λ4) increase. Further, when the weather condition deteriorates and the power of the signal light λ1 decreases to a level that cannot be recognized as a signal, and the signal light λ1 is in a disconnected state (state 3), another signal is output from the optical amplifier 19b. The increase in light (λ2, λ3, λ4) reaches a maximum. In the above discussion, in order to simplify the discussion, it is assumed that there is no wavelength dependence of the gain of the optical amplifier.

  In the signal light (λ2, λ3, λ4) having an increased power level, the waveform deteriorates or noise is generated due to the influence of the nonlinear phenomenon in the optical fiber 23d on the downstream side of the optical amplifier 19b. Degradation of transmission quality is caused. In addition, if the increase in power level exceeds the allowable rated input value of various optical devices such as photodiodes on the receiving side, these devices may be destroyed, increasing the reliability of equipment operation. It will deteriorate significantly.

  In order to solve the above problems, as a method for controlling the optical amplifier in the optical add / drop apparatus, a method for performing constant gain control and constant gain control instead of the above-described constant total output control has been proposed. Yes. (Patent Document 1, Patent Document 2, etc.). In an optical amplifier with a constant gain control, the gain is kept constant, not the output, so even if some of the wavelength-multiplexed signals disappear, the gain in the remaining signal light remains retained. As a result, the output of the remaining signal light can be kept constant.

  However, in the constant gain control, a special mechanism is required to measure the gain of the optical amplifier, an expensive optical component such as an optical attenuator is required, or if the gain is kept constant, the optical amplifier itself As a result, there is a problem that the price of the entire apparatus increases.

  As another method for solving the above problem, a method using compensation light has been proposed. When compensation light is newly applied to the main signal light that is added and dropped in the optical add / drop device, and the power level fluctuates in the main signal light, the power of the compensation light is increased or decreased following the fluctuation. By keeping the overall power constant, it is possible to reduce the power fluctuation of other signal light wavelength-multiplexed. In the method using the compensation light, there are significant problems such as aligning the wavelengths of the compensation light and the main signal light, and requiring compensation light sources as many as the number of signals to be added. Patent Document 3 proposes a method for solving the problem of wavelength control and the number of compensation light sources by slicing spontaneous emission light generated from an optical amplifier installed separately from the original optical amplifier with a filter or the like. Yes.

However, even in this method, there is a problem that the price of the entire apparatus is increased in that an extra expensive optical amplifier is required.
The present invention provides a method for suppressing the influence on other wavelength multiplexed signals even when power level fluctuations or signal interruptions occur in spatial transmission, by using an optical add / drop apparatus having an inexpensive configuration.

  In order to solve the above problem, the first invention of the present application provides a configuration in which at least one signal light branched from the first wavelength multiplexed signal by the optical branching means in the optical add / drop device is the first signal light. At least one or more signal lights transmitted by the optical space transmission apparatus and received from the other second optical space transmission apparatus facing each other are transmitted in the first wavelength multiplexed signal by the optical insertion means in the optical add / drop apparatus. In the optical transmission device to be inserted into the optical add-drop device, an optical amplifier for keeping the power level of the signal received from the second optical space transmission device constant, the optical insertion means of the optical add-drop device and the first optical space transmission device In addition, when the signal light from the second optical space transmission device is in a signal disconnection state, the signal light branched from the first wavelength multiplexed signal is looped back by the optical branching means. The light insertion An optical transmission device comprising a loopback optical switch for insertion into a second wavelength division multiplexed signal by a stage between the optical spatial transmission device and the first spatial optical transmission device It is.

  In addition, the configuration provided by the second invention of the present application is that the point where the optical add / drop device and the first optical space transmission device are installed is the first point, and the second optical space transmission device is The second point is the point where is installed, and is connected to the optical add / drop device via the first wavelength multiplexed signal or the second wavelength multiplexed signal, and the signal from the second optical space transmission device is The loopback optical switch in the optical add / drop device at the first point executes a loopback when a point where a receiver or a transceiver for receiving and converting into an electrical signal is set as a third point. An optical transmission device comprising means for notifying the receiver or the optical transceiver at the third point of the fact that the above has been done.

  According to the first invention of the present application, even when the signal power level from the other optical space transmission device that is opposite is fluctuated, the signal light power level is kept constant by the newly provided optical amplifier. Thus, it is possible to avoid the influence of level fluctuations that occur in wavelength multiplexed signals other than the signal wavelength to be added by branching with an inexpensive apparatus configuration.

  In addition, even when the signal from the other optical space transmission device facing the other side is disconnected, the signal branched from the first wavelength multiplexed signal is looped back by the newly provided optical switch for loop back. By inserting the second wavelength multiplexed signal into the second wavelength multiplexed signal, it is possible to avoid the influence of the level fluctuation generated in the wavelength multiplexed signal other than the signal wavelength to be added by branching with an inexpensive apparatus configuration.

  Further, according to the second invention of the present application, the trouble on the physical layer (the influence on other wavelength multiplexed signals) due to the power level fluctuation which is the effect of the first invention is avoided, and at the same time, the trouble occurs on the upper layer. Thus, it is possible to avoid the influence caused by the occurrence of a logical loop on the network.

  Embodiments will be described in detail below.

  A first embodiment of the present invention will be described with reference to FIG. Node 1 (51) is one of the nodes in the wavelength division multiplexing network. In node 1 (51), one wavelength (λ1) is branched and inserted from the wavelength division multiplexed signals (λ1, λ2, λ3, λ4). The node 2 (52) and the node 1 (51) constitute an optical space transmission network via the space transmission path (53), and the signal light (λ1) branched (dropped) at the node 1 (51) is left as it is. Spatial transmission is performed toward the node 2 (52). Further, the signal light (λ1 ′) transmitted from the node 2 (52) is directly inserted (added) into the wavelength multiplexed signal at the node 1 (51).

  Here, in order to clearly indicate that the wavelength λ1 and the wavelength λ1 ′ are the same wavelength, but are different as signals, a signal directed from the node 1 (51) to the node 2 (52) is represented by λ1 and the node 2 ( 52) from the node 1 to the node 1 (51) are distinguished from each other as λ1 ′.

  In this embodiment, the wavelength division multiplexing network has a line from the left to the right in the figure (fibers 54a and 54b), a line from the right to the left in the figure (fiber 54c and fiber 54d), and two lines for uplink and downlink. ing. In the node 1, the signal light λ1 is branched (dropped) on the line side from the left to the right in the drawing, and is inserted (added) on the line side from the right to the left in the drawing.

  The flow of the signal light will be described in detail. The wavelength multiplexed signals (λ1, λ2, λ3, λ4) reaching the node 1 (51) from the optical fiber 54c are demultiplexed by the optical demultiplexer 55a, and are individually separated for each wavelength. Output from the output port. Of these, the signal light λ1 is selected by the optical branching switch 56a as to whether it passes (through) or branches (drops) out of the two outputs, but here the branch (drop) side is selected. . The remaining three wavelengths of signal light (λ2, λ3, λ4) are combined by the optical multiplexer 58a to form a wavelength multiplexed signal, and enter the optical fiber 54a through the optical amplifier 60a.

  The signal light λ1 is branched from the optical branching switch 56a and reaches the optical coupler 65. The optical coupler 65 distributes the input signal light λ1 from the two output ports at an appropriate distribution ratio and outputs the result. One of the signal light λ1 output from the optical coupler 65 reaches the transmission optical system 62a for spatial transmission, and the other signal light λ1 reaches the loopback optical switch 68 via the loopback optical line 66. Among these, the signal light λ 1 that has reached the transmission optical system 62 a is emitted to the spatial transmission path 53. As a result, the signal light λ1 transmitted from the node 1 (51) reaches the node 2 (52) via the spatial transmission path 53, is collected by the reception optical system 63a, and is electrically signaled by the optical wireless receiver 64a. Is converted to output.

  Similarly, on the node 2 (52) side, signal light of wavelength λ1 'is formed by the optical wireless transmitter 61b and emitted from the transmission optical system 62b to the optical space transmission line 53. As described above, the wavelength λ1 and the wavelength λ1 'are the same wavelength, but are shown separately to clearly indicate that they are different as signals. The signal light λ1 'transmitted from the node 2 (52) reaches the node 1 (51) and is collected by the receiving optical system 63b. The collected signal light λ 1 ′ reaches the optical coupler 67. The optical coupler 67 distributes the input signal light λ1 'from the two output ports at an appropriate distribution ratio and outputs the result. One of the signal light λ1 'output from the optical coupler 67 reaches the loopback optical switch 68, and the other signal light λ1' reaches the optical power monitor light receiver 71.

  The loopback optical switch 68 selects and outputs either the signal light λ1 output from the optical coupler 65 or the signal light λ1 ′ output from the optical coupler 67. The signal light λ1 or λ1 ′ output from the loopback optical switch 68 is distributed at an appropriate distribution ratio in the optical coupler 70 via the optical amplifier 69, and one of the distributed signal light λ1 or λ1 ′ is optically inserted. Switch 57b is reached. The other signal light λ <b> 1 or λ <b> 1 ′ distributed by the optical coupler 70 reaches the optical power monitor light receiver 73.

  The optical power monitor light receiver 71 outputs an electrical signal corresponding to the input power level to the optical switch control circuit 72, and the optical switch control circuit 72 controls the loopback optical switch 68 based on the electrical signal.

  The optical power monitor light receiver 73 outputs an electrical signal corresponding to the input power level to the optical amplifier control circuit 74, and the optical amplifier control circuit 74 controls the optical amplifier 69 based on the electrical signal.

  The optical insertion switch 57b passes (through) the signal λ1 transmitted from the fiber 54b side, or inserts (adds) the signal λ1 or λ1 ′ that has passed through the loopback optical switch 68 and the optical amplifier 69. Here, the insertion (add) side is selected. Therefore, the signal λ1 or λ1 ′ that has passed through the loopback optical switch 68 and the optical amplifier 69 reaches the optical multiplexer 58b via the optical insertion switch 57b, and is demultiplexed from the optical demultiplexer 55b. The two signal lights (λ2, λ3, λ4) are combined to form a wavelength multiplexed signal, which enters the optical fiber 54b through the optical amplifier 60b.

  Here, how the above configuration operates when a failure occurs in the spatial transmission path will be described. As described above, the optical switch control circuit 72 controls the loopback optical switch 68 in accordance with the power level detected by the optical power monitor light receiver 71. Specifically, control as shown in the sequence diagram of FIG. 8 is performed.

  First, as an initial state, the loopback optical switch 68 is switched to the optical coupler 67 side, and the signal λ1 ′ transmitted from the node 2 (52) passes through the loopback optical switch 68 and is optically switched. The insertion switch 57b is inserted into the wavelength multiplexed signal.

  Here, the power level detected by the optical power monitoring light receiver 71 is compared with a certain specified value 1. The specified value 1 is set to a value corresponding to determining that the spatial transmission line is disconnected. When the power level is larger than the specified value 1, the loopback optical switch 68 is kept as it is and the power level is continuously monitored. However, when the power level is smaller than the specified value 1, the loopback optical switch is switched to the optical coupler 65 side, and the signal λ1 branched by the optical branching switch 56a of the node 1 (51) is turned back. (After looping back), the optical add switch 57b changes to a state of being inserted into the wavelength multiplexed signal. That is, when the spatial transmission line is disconnected, the signal branched (dropped) at the node 1 (51) is looped back as it is and inserted (added) at the node 1 (51).

  On the other hand, the optical amplifier control circuit 74 controls the optical amplifier 69 so that the signal from the optical power monitoring light receiver 73 is always constant. That is, the optical amplifier 69 is subjected to constant output control.

  Here, it is assumed that the loss increases in the optical space transmission path 53 due to the influence of weather conditions and the like. Then, as described above, the power level of the signal λ1 ′ is reduced. However, since the output of the optical amplifier 69 is kept constant, even if the weather conditions deteriorate after the output of the optical amplifier 69, Power level is kept constant. Therefore, the power level of the wavelength multiplexed signal after the signal λ1 ′ is inserted is also kept constant. As a result, even if the power level of the signal λ1 ′ fluctuates on the spatial transmission path, the output of the optical amplifier 60b The influence on the wavelengths (λ2, λ3, λ4) is prevented.

  Further, it is assumed that communication interruption occurs in the optical transmission path 53 due to further deterioration of weather conditions. Then, the reception optical system 63b of the node 1 (51) cannot receive the signal, and the signal is interrupted. However, when the signal disconnection occurs, the optical switch control circuit 72 detects this, and the loopback optical switch 68 is switched, and the signal λ1 branched from the optical branching switch 56a is looped back as it is, and the optical insertion switch 57b. Will be inserted. The power level of the signal λ1 inserted by the optical insertion switch 57b is controlled to the same value as the power level of the signal λ1 ′ inserted before the loopback is performed by the output constant control of the optical amplifier 69. ing. Therefore, the power level of the wavelength-division multiplexed signal after the signal λ1 is inserted is also kept constant. As a result, even if the signal λ1 ′ is disconnected on the spatial transmission path, The influence on the wavelengths (λ2, λ3, λ4) is prevented.

  As described above, the loopback optical switch 68 and the optical amplifier 69 prevent the influence on the wavelength multiplexed signals (λ2, λ3, λ4) other than the signal λ1 even if a failure occurs in the spatial transmission path. It becomes possible.

  Returning again to the sequence diagram of FIG. Once the loopback is executed and the loopback switch 68 is switched to the optical coupler 65 side, the power level detected by the optical power monitor light receiver 71 is compared with a predetermined value 2 this time. . The specified value 2 is set to a value equivalent to determining that the spatial transmission path has been recovered. It is possible to set the same value as the prescribed value 1, or to a value higher than the prescribed value 1 in consideration of the stability of the apparatus (in consideration of hysteresis).

  If the power level is smaller than the specified value 2, the power level is continuously monitored with the loopback optical switch 68 as it is (while being looped back). However, when the power level is higher than the specified value 2, the loopback optical switch is switched to the optical coupler 67 side, and the signal λ1 ′ spatially transmitted from the node 2 (52) is allowed to pass therethrough. The switch 57b restores the state (initial state) for insertion into the wavelength multiplexed signal.

  As shown in FIG. 1, one output of the optical coupler 65 is connected to the loopback optical switch 68, and the other output is connected to the transmission optical system 62a. As a result, communication toward the node 2 (52) is maintained, and when the cause of communication disconnection (deterioration of weather conditions, etc.) in the spatial transmission path 53 is improved and the line is restored, the communication is received again. The signal λ1 ′ starts to be input to the optical system 63b.

  Therefore, when the line of the spatial transmission path 53 is restored and the signal λ1 ′ starts to be input to the receiving optical system 63b, the optical switch control circuit 72 detects this, and the loopback optical switch 68 is moved to the spatial transmission side. Then, the signal λ1 ′ is switched back to the initial state where it is inserted at the node 1 (51). Of course, the power level fluctuation at the time of restoration is also absorbed by the optical amplifier 69 and does not affect other wavelengths (λ2, λ3, λ4). As described above, by applying the present invention, not only the influence when the signal interruption occurs but also the signal λ1 ′ from the spatial transmission line is automatically restored even when the signal interruption is recovered. It becomes possible.

  In the above description, the optical amplifier 59a, the optical amplifier 59b, the optical amplifier 60a, and the optical amplifier 60b are installed immediately after input and immediately before output of the optical add / drop device. The present invention is applicable even when either the amplifier or the output side optical amplifier is missing. If the entire network has at least one optical amplifier that collectively amplifies wavelength-multiplexed signals, the effect of the present invention, that is, the effect of not affecting other signals even if a failure occurs in the spatial transmission path, is obtained. It is possible.

  In the above description, as a basic configuration of the optical add / drop apparatus, one wavelength (λ1) is transmitted from one of the two upstream and downstream lines in a wavelength multiplexed signal in which four wavelengths (λ1, λ2, λ3, λ4) are multiplexed. The configuration of branching and inserting one wavelength (λ1 ′) into the other line was considered, but the configuration of the optical add / drop device may take various forms depending on the network configuration. The present invention is applicable to various configurations of such optical add / drop devices. For example, as a matter of course, the number of wavelengths is not limited to four, and can be adapted to any number of wavelengths. The number of wavelengths to be added / dropped is also arbitrary, and it is possible to cope with any number of added / dropped units by installing in parallel the number of wavelengths related to the processing of λ1 and λ1 ′ described in this embodiment. .

  The optical branch switch 56 and the optical add switch 57 use separate 1-input 2-output switches or 2-input 1-output switches in this embodiment, but they may be integrated by using 2-input 2-output switches. Is possible. It is not necessarily a switch, it can be replaced with a circuit board using an optical adapter and a patch cable, and if there is no need to change the network configuration (change of branching and passing, or changing of insertion and passing), switching There is no problem even if the structure is always branched or inserted as one input and one output without providing a mechanism for the above.

  As a basic configuration of the optical add / drop apparatus, FIG. 1 illustrates a mode in which each wavelength port is connected with the collective optical demultiplexer 55 and the collective optical multiplexer 60 facing each other. The array type waveguide grating (AWG) is well known as such a batch type device. However, the present invention can be applied not only to a configuration using a collective multiplexer / demultiplexer but also to an optical add / drop device using a wavelength selective type three-terminal element such as a combination of a fiber Bragg grating and a circulator, or a filter. is there.

  In the above description, a configuration is considered in which one wavelength (λ1) is branched from one of two upstream and downstream lines, and one wavelength (λ1 ′) is inserted into the other line. The present invention can be applied with the configuration shown in FIG.

  The operation principle of the embodiment shown in FIG. 9 is the same as that of FIG. That is, the output branched from the optical branching switch 56 is distributed by the optical coupler 65, one is connected to the node 2 (52) via the transmission optical system 62a, and the other is connected to the loopback optical switch 68. A signal from the node 2 is distributed by an optical coupler 67 through a receiving optical system 63b, one of which is connected to the loopback optical switch 68 and the other is connected to a light receiver 71 for monitoring the optical power level. The loopback optical switch 68 is controlled by the optical switch control circuit 72, and its sequence is as shown in FIG. The output of the loopback optical switch is input to an optical amplifier 69 whose output is controlled to be constant by an optical amplifier control circuit 74 and an optical power level monitor photoreceiver 73, passes through an optical coupler 70, and is wavelength multiplexed by an optical insertion switch 57. Inserted into the signal.

  When the present invention is not applied, output fluctuation occurs in the signal light (λ2, λ3, λ4) according to the loss fluctuation in the spatial transmission path 53 at the output of the amplifier 61. However, the output fluctuation can be controlled by the functions of the loopback optical switch 68 and the optical amplifier 69.

  An embodiment according to the second invention of the present application is shown in FIG. FIG. 10 is a configuration in which the node 3 (81) is added to the configuration of FIG. 1, and the optical transmission in the node 3 (81) is transmitted from the optical switch control circuit (72) in the node 1 (51). In this configuration, loopback execution / release notification means 84 is provided for one or both of the receiver 82 and the optical receiver 83.

  The signal λ1 output from the optical transmitter 82 in the node 3 (81) is inserted into the wavelength multiplexed signal through the optical add switch 57c and the optical multiplexer 58c, and is incident on the optical fiber 54c. When the wavelength multiplexed signal reaches the node 1 (51), it is amplified by the optical amplifier 59a and then demultiplexed for each wavelength by the optical demultiplexer 55a, and the signal λ1 is branched by the optical branching switch 56a. The output branched from the optical branch switch 56a is distributed by the optical coupler 65, one of which is connected to the node 2 (52) through the transmission optical system 62a, and the other is connected to the loopback optical switch 68. A signal from the node 2 is branched by an optical coupler 67 through a receiving optical system 63b, one of which is connected to the loopback optical switch 68 and the other is connected to a light receiver 71 for monitoring the optical power level. The loopback optical switch 68 is controlled by the optical switch control circuit 72. The output of the loopback optical switch 68 is input to the optical amplifier 69 whose output is controlled to be constant by the optical amplifier control circuit 74 and the optical power level monitoring light receiver 73, and passes through the optical coupler 70, through the optical insertion switch 57 b and the optical coupling. It is inserted into the wavelength multiplexed signal by the waver 58b and is incident on the fiber 54b. The signal reaching the node 3 (81) is branched by the optical demultiplexer 55d and the optical branching switch 56d and reaches the optical receiver 83.

  Further, from the optical switch control circuit 72, a loopback execution / release notification means 84 is connected to one or both of the optical transmitter 82 and the optical receiver 83 in the node 3 (81). The optical switch control circuit 72 controls the optical switch and performs communication using the notification means 84 in accordance with the sequence diagram shown in FIG.

  When communication interruption occurs in the spatial transmission path 53, the optical switch control circuit 72 switches the loopback optical switch 72 to the optical coupler 65 side to loop back the branched signal λ1, and at the same time, the optical transmitter 82 and the optical receiver. Notify one or both of the machines 83 that the loopback has been executed. When the communication on the spatial transmission path 53 is restored, the optical switch control circuit 72 switches the loopback optical switch 72 to the optical coupler 67 side and switches to the initial state in which the signal λ1 ′ transmitted in space is inserted. At the same time, one or both of the optical transmitter 82 and the optical receiver 83 are notified that the loopback has been canceled.

  When there is no loopback execution / release notification means 84, the optical receiver 83 of the node 3 (81) has detected the signal λ1 ′ in the normal state, but the occurrence of signal interruption in the spatial transmission path, loop Simultaneously with the back execution, the signal λ1 from the optical transmitter 82 is detected. Depending on the design of the optical receiver 83 or the protocol of the network connected to the optical transmitter 82 or optical receiver 83, the loop There is a possibility that troubles occur. However, the loopback execution and release notification means 84 allows the loopback execution and release at the node 1 (51) to be performed by either the optical transmitter 82 or the optical receiver 83 of the node 3 (81), or both. To avoid problems on the physical layer due to power fluctuations (effects on other wavelength multiplexed signals) and at the same time troubles that occur on higher layers (effects associated with the occurrence of logical loops on the network) Can also be avoided.

  As such a loopback execution / cancellation notification means 84, it is conceivable to multiplex this notification signal in the monitoring signal of the apparatus as shown in FIG. In FIG. 12, a monitor signal transmitter / receiver 85 a is installed at node 1 (51), and a monitor signal transmitter / receiver 85 b is installed at node 3 (81), and both are connected by a monitor signal communication path 86. In general, an optical add / drop device or an optical amplifier device (optical repeater) is provided with such a communication path dedicated to device monitoring, in addition to the main data line. By multiplexing this loopback execution / cancellation notification signal in a part of the band of the monitoring signal, notification between the devices can be easily realized, and then either the transmitter 82 or the receiver 83 or its By connecting both to the monitoring signal transmitter / receiver 85b, it is possible to notify execution or cancellation of the loopback.

  In FIG. 12, the monitoring signal path 86 is represented by an image in which a dedicated fiber or electric cable for monitoring signals is installed, but the monitoring signal path 86 does not need to be physically independent, and the monitoring signal is included in the main signal light. This can also be realized by a method of multiplexing light. Actually, in the case of a long-distance transmission device, dedicated monitoring signal light is often further wavelength-multiplexed with the main signal. As the monitoring signal light, a wavelength outside the band of the wavelength multiplexed signal (for example, light in the vicinity of 1500 nm or 1510 nm) is used. In the case of an Ethernet (registered trademark) device or an IP device, a method in which a monitoring signal (for example, SNMP: Simple Network Management Protocol) as a protocol is packet-multiplexed with a main signal is often used. In this way, it is possible to notify the execution or cancellation of loopback using a signal that is wavelength-multiplexed with respect to the main signal or a monitoring signal that is time-multiplexed or packet-multiplexed with respect to the main signal.

The figure which shows the Example in 1st invention of this application. The figure which shows the structural example of an optical space transmission apparatus. The figure which shows the structural example of an optical add / drop apparatus. The figure which shows the structural example of the network using an optical add / drop apparatus. The figure which shows the example 1 of a coupling | bonding of an optical add-drop apparatus and an optical space transmission apparatus. The figure which shows the example 2 of a coupling | bonding of an optical add-drop apparatus and an optical space transmission apparatus. The figure explaining the output fluctuation | variation in the optical amplifier for wavelength multiplexing. The sequence diagram in the 1st invention of this application. The figure which shows another Example in 1st invention of this application. The figure which shows the Example in 2nd invention of this application. The sequence diagram in the 2nd invention of this application. The figure which shows another Example in 2nd invention of this application.

Explanation of symbols

1, 2 ... Optical space transmission device,
3. Spatial transmission line,
4a, 4b ... optical wireless transmitter,
5a, 5b ... transmission optical system,
6a, 6b ... receiving optical system,
7a, 7b ... optical wireless receiver,
11 ... Optical add / drop device,
12, 12a, 12b, 12c, 12d ... optical demultiplexer,
13, 13a, 13b, 13c, 13d ... optical branching switch,
14, 14a, 14b, 14c, 14d ... optical insertion switch,
15, 15a, 15b, 15c, 15d ... optical multiplexer,
16, 16a, 16b ... optical transmitter,
17, 17a, 17b ... optical receiver,
18, 18a, 18b ... optical amplifier,
19, 19a, 19b ... optical amplifier,
21 ... Optical add / drop device (node A),
22: Optical add / drop device (Node B),
23, 23a, 23b, 23c, 23d, 22e, 23f ... optical fiber,
24: Optical add / drop device (node A),
25. Optical space transmission device (node C),
26: Optical add / drop device (node A),
27: Optical space transmission device (node C),
51. Optical add / drop device (node 1),
52 ... Optical space transmission device (node 2),
53. Optical space transmission line,
54, 54a, 54b, 54c, 54d ... optical fiber,
55, 55a, 55b, 55c, 55d ... optical multiplexer,
56, 56a, 56b, 56c, 56d ... optical branching switch,
57, 57a, 57b, 57c, 57d ... optical insertion switch,
58, 58a, 58b, 58c, 58d ... optical demultiplexer,
59, 59a, 59b ... optical amplifier,
60, 60a, 60b ... optical amplifier,
61, 61a, 61b ... optical wireless transmitter,
62, 62a, 62b ... transmission optical system,
63, 63a, 63b ... receiving optical system,
64, 64a, 64b ... optical wireless receiver,
65: Optical coupler,
66 ... optical path for loopback,
67 ... Optical coupler,
68. Optical switch for loopback,
69: Optical amplifier,
70: Optical coupler,
71 ... Optical power monitor receiver,
72. Optical switch control circuit,
73: Optical power monitor light receiver 74: Optical amplifier control circuit,
81 ... Node C,
82: Optical transmitter,
83: Optical receiver,
84 ... Notification means for loopback execution and release,
85a, 85b ... monitoring signal transceiver,
86: Monitoring signal communication path.

Claims (10)

A first optical add / drop device comprising optical branching means for branching signal light having at least one wavelength from wavelength multiplexed signal light transmitted in a first direction;
A second optical add / drop device comprising an optical insertion means for inserting a signal light having at least one wavelength into the wavelength multiplexed signal light transmitted in the second direction;
A first optical space transmission device having an optical transmitter for transmitting the signal light branched by the optical branching unit to the outside;
Transmitting from a second optical space transmission device having a function of receiving signal light transmitted from the first optical space transmission device and having a function of transmitting signal light to the first optical space transmission device An optical receiver for receiving the signal light
An optical amplifier for keeping the power level of the signal light received from the second optical space transmission device at a predetermined value is provided between the optical insertion unit and the optical transmission unit,
Further, when the signal light transmitted from the second optical space transmission device is in a signal disconnection state, the signal light branched from the wavelength multiplexed signal transmitted in the first direction by the optical branching means A loopback optical switch for inserting into the wavelength division multiplexed signal transmitted in the second direction by transmitting the looped back signal light to the optical insertion means; and An optical transmission apparatus provided between the optical receiver and the optical receiver. The point where the optical add / drop device and the first optical space transmission device are installed is the first point,
The point where the second optical space transmission device is installed is the second point,
An optical receiving unit or an optical transmission / reception unit that receives a signal from the second optical space transmission device and converts it into an electrical signal is installed, and wavelength multiplexed signal light transmitted in the first direction with the optical add / drop device Alternatively, when the point connected via the wavelength multiplexed signal light transmitted in the second direction is the third point,
Means for notifying the optical receiver or optical transmitter / receiver at the third point that the loopback optical switch provided in the optical add / drop device at the first point has executed the loopback; The optical transmission device according to claim 1.   The loopback optical switch releases the loopback when the signal light from the second optical space transmission device returns from the signal disconnection state, and the signal light from the second optical space transmission device. 2. The optical transmission device according to claim 1, wherein control is performed so that the optical signal is passed from the optical receiving unit to the optical insertion unit. Power level monitoring means for monitoring the power level of the signal light transmitted from the second optical space transmission device is provided between the optical receiver connected to the loopback optical switch and the loopback optical switch. ,
When the power level amount detected by the power level monitoring means is lower than the first specified value, the loopback optical switch is set to the loopback side, while the power level monitoring means is detected by the power level monitoring means. 2. The optical transmission device according to claim 1, wherein when the power level amount is higher than the second specified value, the loopback of the loopback optical switch is canceled.   3. The optical transmission apparatus according to claim 2, wherein a signal for monitoring a device of an optical add / drop apparatus or an optical amplifier is used as the notification means.   6. The optical transmission apparatus according to claim 5, wherein a monitoring signal wavelength-multiplexed with the main signal light is used as the apparatus monitoring signal according to claim 5.   6. The optical transmission device according to claim 5, wherein a monitoring signal time-multiplexed with the main signal light or a monitoring signal multiplexed with a packet is used as the device monitoring signal according to claim 5. Optical branching means for branching signal light having at least one wavelength from wavelength multiplexed signal light transmitted on the optical transmission path, and at least one wavelength multiplexed signal light transmitted on the optical transmission path provided with the optical branching means An optical add / drop device having optical insertion means for inserting signal light having one wavelength,
A first optical space transmission device having an optical transmitter for transmitting the signal light branched by the optical branching unit to the outside;
Transmitting from a second optical space transmission device having a function of receiving signal light transmitted from the first optical space transmission device and having a function of transmitting signal light to the first optical space transmission device An optical receiver for receiving the signal light
An optical amplifier for keeping the power level of the signal light received from the second optical space transmission device at a predetermined value is provided between the optical insertion unit and the optical transmission unit,
Further, when the signal light transmitted from the second optical space transmission device is in a signal interruption state, the signal light branched from the wavelength multiplexed signal transmitted on the optical transmission path by the optical branching means is looped. A loopback optical switch for inserting the signal light that is backed back and looped back into the wavelength division multiplexing signal transmitted on the optical transmission path by transmitting the signal light to the optical insertion unit; An optical transmission device provided between the receiving unit and the receiver.   The loopback optical switch releases the loopback when the signal light from the second optical space transmission device returns from the signal disconnection state, and the signal light from the second optical space transmission device. 9. The optical transmission device according to claim 8, wherein switching is performed so that the optical signal passes from the optical receiving unit to the optical insertion unit. A power level monitoring means for monitoring the power level of the signal light transmitted from the second optical space transmission device is provided between the optical receiver connected to the optical switch for loopback and the optical switch for loopback. Prepared,
When the power level amount detected by the power level monitoring means is lower than the first specified value, the loopback optical switch is set to the loopback side, while the power level monitoring means is detected by the power level monitoring means. 9. The optical transmission apparatus according to claim 8, wherein when the power level amount is higher than the second specified value, the loopback of the loopback optical switch is canceled.

Images