Optical transmission device
An optical transmission device capable of preventing deterioration in the transmission quality of a signal beam. A wavelength-multiplexed signal beam from a transmission path is split by a splitter, and the split signal beams are input to first and second optical paths, respectively. An add/drop unit for adding/dropping a wavelength-multiplexed signal beam is removably insertable in the second optical path. A switch outputs the wavelength-multiplexed signal beam, received from one of the first and second optical paths, to an optical amplifier. The optical amplifier amplifies the wavelength-multiplexed signal beam output from the switch and outputs the amplified signal beam to a subsequent circuit. A supervisory controller collects alarm information from the optical transmission device as well as from other optical transmission devices, and controls the switch in accordance with the collected alarm information such that the wavelength-multiplexed signal beam from the second optical path is input to the optical amplifier.
1. An optical transmission device for transmitting a wavelength-multiplexed optical signal, comprising:
a first optical path;
a second optical path in which an add/drop unit for adding/dropping a wavelength-multiplexed optical signal is removable;
a splitter for splitting a wavelength-multiplexed optical signal received from a transmission path and outputting the split optical signals to the first and second optical paths, respectively;
a switch for selecting one of the wavelength-multiplexed optical signals received from the first and second optical paths, and outputting the selected wavelength-multiplexed optical signal to an optical amplifier; and
a supervisory controller for collecting alarm information from the optical transmission device or in a different optical transmission device, and controlling the switch in accordance with the alarm information such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier.
2. The optical transmission device according to claim 1 , wherein, if the alarm information is received after the switch is controlled such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier, the supervisory controller controls the switch such that the wavelength-multiplexed optical signal from the first optical path is input to the optical amplifier.
3. The optical transmission device according to claim 1 , wherein, when controlling the switch such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier, the supervisory controller transmits, to the different optical transmission device, switchover information indicating switchover of the optical paths.
4. The optical transmission device according to claim 3 , wherein, when the switchover information is received, the different optical transmission device masks output of the alarm information.
5. The optical transmission device according to claim 4 , wherein the supervisory controller transmits, to the different optical transmission device, control completion information indicating that control of the switch is completed, and
when the control completion information is received, the different optical transmission device cancels the masking of the alarm information.
6. The optical transmission device according to claim 3 , wherein the different optical transmission device has an OUPSR function and, on receiving the switchover information, does not cause the optical unidirectional path switched ring (OUPSR) to perform redundancy switching.
7. The optical transmission device according to claim 6 , wherein, if a signal interruption continues for a time longer than an expected interruption time over which the wavelength-multiplexed optical signal is expectedly interrupted by the switch, the different optical transmission device causes the OUPSR to perform redundancy switching.
8. The optical transmission device according to claim 3 , wherein the different optical transmission device has a span switch function and, on receiving the switchover information, does not cause the span switch to perform switching.
9. The optical transmission device according to claim 1 , wherein the switch is a 2×2 switch having inputs connected to the first and second optical paths, respectively, and having outputs respectively connected to the optical amplifier and an optical level detector for detecting an optical level of the wavelength-multiplexed optical signal.
10. The optical transmission device according to claim 9 , wherein the supervisory controller detects the optical level of an output of the add/drop unit inserted in the second optical path by controlling the 2×2 switch such that the second optical path is connected to the optical level detector, and controls switchover of the 2×2 switch in accordance with the detected optical level and the alarm information such that the second optical path is connected to the optical amplifier.
11. The optical transmission device according to claim 9 , wherein, if a difference between the optical level of the wavelength-multiplexed optical signal input to the optical amplifier and the optical level of an output of the add/drop unit detected by the optical level detector is smaller than a predetermined value, the supervisory controller controls switchover of the 2×2 switch such that the second optical path is connected to the optical amplifier.
12. The optical transmission device according to claim 11 , wherein the supervisory controller measures in advance a loss caused by the 2×2 switch, and has the measured loss reflected in the optical level of the output of the add/drop unit detected by the optical level detector.
13. The optical transmission device according to claim 9 , wherein the supervisory controller calculates an optical level per wavelength from the number of wavelengths handled by the add/drop unit inserted in the second optical path, acquired from the add/drop unit or a supervisory control terminal, and the optical level of the add/drop unit detected by the optical level detector.
14. The optical transmission device according to claim 9 , wherein, if, after the 2×2 switch is controlled such that the second optical path is connected to the optical amplifier, the 2×2 switch should be returned to a state such that the first optical path is connected to the optical amplifier, the supervisory controller calculates an optical level per wavelength from the number of wavelengths acquired from a supervisory control terminal and the optical level of the wavelength-multiplexed optical signal from the first optical path detected by the optical level detector.
15. The optical transmission device according to claim 1 , wherein, if wavelength count information received from the different optical transmission device or a supervisory control terminal disagrees with that acquired from the add/drop unit, the supervisory controller controls the switch such that the wavelength-multiplexed optical signal from the first optical path is input to the optical amplifier.
16. The optical transmission device according to claim 1 , wherein the supervisory controller calculates an optical level per wavelength from an optical level of an output of the add/drop unit and wavelength count information received from a supervisory control terminal and, if the calculated optical level is at a predetermined level, controls the switch such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier.
17. The optical transmission device according to claim 1 , wherein the supervisory controller collects signal degradation information about signal degradation caused in an add/drop unit of the different optical transmission device, and controls the switch in accordance with the signal degradation information such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier.
18. The optical transmission device according to claim 1 , wherein the optical amplifier performs automatic level control and automatic gain control, and
when controlling the switch such that the wavelength-multiplexed optical signal from the second optical path is input to the optical amplifier, the supervisory controller switches control mode of the optical amplifier from the automatic level control to the automatic gain control.
19. The optical transmission device according to claim 1 , wherein the supervisory controller acquires, from the add/drop unit or a supervisory control terminal, the number of wavelengths after switchover control of the switch, and transmits the acquired number of wavelengths to the different optical transmission device.
20. The optical transmission device according to claim 19 , wherein the optical transmission device and the different optical transmission device each include an ASE calculation for calculating an amount of change of amplified spontaneous emission (ASE) from the acquired number of wavelengths before the switch is switched.