Light branching/inserting apparatus and light branching apparatus using wavelength selection filter

• US 6,538,782 B1
• Filed: 05/12/1998
• Issued: 03/25/2003
• Est. Priority Date: 02/02/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Onaka, Hiroshi, Chikama, Terumi, Otsuka, Kazue
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Bello, Agustin
• Application Number:
  US09/076,068
• Time in Patent Office: 1,778 Days
• Field of Search: 359/124-134, 359/161, 359/110
• US Class Current: 398/82
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant

Abstract

A light branching/inserting apparatus which can easily control light signal wavelengths, and which can branch, insert or transmit light signals having an optional wavelength and optional multiplexed number, by using a wavelength selection filter utilizing acousto-optic effects. The apparatus comprises; an ADM node section 10 which has an AOTF 11 with four ports as a wavelength selection filter and is connected to a transmission path, an RF signal generator 20 which generates an RF signal of an optional frequency and applies the signal to the AOTF 11, a selected wavelength-variable light branching section 30 which receives and processes the light signal output from the branching port of the AOTF 11 for each wavelength, a light inserting section 40 which generates an optional number of insertion light signals with optional wavelengths and sends the insertion light signals to an insertion port of the AOTF 11, and a monitoring section 50 which monitors the spectrum of the light signal input/output to/from the ADM node section 10.

Claims

1. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output,

a branching port connected to said light branching means and

an insertion port connected to said light inserting means, and

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port, and

said branching/inserting means further comprises a monitoring means for respectively measuring a spectrum of the light signal input from said transmission path to said input port of said wavelength selection filter and a spectrum of the light signal output from said output port of said wavelength selection filter to said transmission path, to monitor the light power of each wavelength and thereby determine whether the wavelength selection filter is operating properly.

2. An apparatus according to claim 1, further comprising at least one light amplifying means for amplifying the light signals transmitted through the transmission path up to a power level required for transmission.

3. An apparatus according to claim 1, further comprising:

dispersion compensation means for compensating for dispersion characteristics of said transmission path, and

dispersion compensation light amplifying means for compensating for a loss of light signal power in said dispersion compensation means.

4. An apparatus according to claim 1, wherein said light branching means includes

a light wave dividing section for dividing the light signal output from the branching port of said wavelength selection filter according to a received number of wavelengths,

a wavelength selecting section in which the selected wavelength is variable, which is provided for each output port of said light wave dividing section and which selects one light wavelength from the wave-divided light signals and outputs the selected light wavelength, and

a reception section for receiving and processing a light wavelength selected by said wavelength selecting section.

5. An apparatus according to claim 1, wherein said light inserting means includes

a light source section for generating light corresponding to all wavelengths which are transmittable on said transmission path;

a light wave mixing/dividing section for wave-dividing the wavelength division multiplexed light in which each light wavelength from said light source section is wave-mixed according to the number of inserted wavelengths and outputting the wavelength division multiplexed light;

an insertion light generating section in which the selected wavelength is variable, which performs modulation for each wavelength division multiplexed light output from said light wave mixing/dividing section and selects and outputs one light wavelength;

a light wave mixing section for mixing a light signal of each wavelength output from said insertion light generating section and outputting the wave-mixed light signals; and

a light amplifying section for amplifying a light signal output from said light wave mixing section and outputting the amplified light signal to the insertion port of said wavelength selection filter.

6. An apparatus according to claim 5, wherein said light inserting means includes

a dispersion compensation section for compensating for the dispersion characteristics of said transmission path, and

a dispersion compensation light amplifying section for compensating for a loss in the light power in said dispersion compensation section.

7. An apparatus according to claim 5, wherein said light inserting means includes a light source control section for sending only a light wavelength which can be inserted, from said light source section to said light wave mixing section.

8. An apparatus according to claim 7, wherein said light inserting means includes an insertion light control section for sending only a light signal of a wavelength to be actually inserted, from said insertion light generating section to said light wave mixing section.

9. An apparatus according to claim 1, wherein with said selection signal at least one of the frequency or output power is adjusted according to monitoring results of said monitoring means, and with said wavelength selection filter, light signal power of each wavelength output from the output port is controlled to be almost constant according to said selection signal.

10. An apparatus according to claim 1, wherein said light inserting means includes a power adjusting section for adjusting the light signal power of each wavelength output from said light inserting means according to monitoring results of said monitoring means.

11. An apparatus according to claim 1, wherein said selection signal has a frequency corresponding to an unused wavelength in the light signal sent to the input port from the transmission path to remove noise generated in the unused wavelength by said wavelength selection filter.

12. An apparatus according to claim 1, further comprising temperature control means for controlling a device temperature of said wavelength selection filter to be almost constant.

13. An apparatus according to claim 1, further comprising temperature monitoring means for measuring a device temperature of said wavelength selection filter, wherein the frequency of said selection signal is corrected based on measurement results of said temperature monitoring means.

14. A light branching/inserting apparatus using a wavelength selection filter, said apparatus being connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path, said apparatus comprising:

light branching means for receiving and processing branched light signals for each wavelength;

light inserting means for generating insertion light to be inserted into the light signals on said transmission path,

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from said transmission path is input, an output port from which a light signal to be output to said transmission path is output, a branching port connected to said light branching means and an insertion port connected to said light inserting means; and

monitoring means for respectively measuring a spectrum of the light signal input from said transmission path to said input port of said wavelength selection filter and a spectrum of the light signal output from said output port of said wavelength selection filter to said transmission path, to monitor the light power for each wavelength and thereby determine whether the wavelength selection filter is operating properly,

wherein said wavelength selection filter branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port.

15. A light branching apparatus using a wavelength selection filter, said apparatus being connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching light signals having at least one wavelength from amongst the light signals on said transmission path, said apparatus comprising:

light branching means for receiving and processing branched light signals for each wavelength;

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from said transmission path is input, an output port from which a light signal to be output to said transmission path is output, and a branching port connected to said light branching means; and

monitoring means for respectively measuring a spectrum of the light signal input from said transmission path to said input port of said wavelength selection filter and a spectrum of the light signal output from said output port of said wavelength selection filter to said transmission path, to monitor the light power for each wavelength and thereby determine whether the wavelength selection filter is operating properly,

wherein said wavelength selection filter branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal sent to the input port from said transmission path and outputs the branched light signal to said branching port.

16. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output, and a branching port connected to said light branching means, and

light wave mixing means for mixing insertion light from said light inserting means into light signals output from said output port and outputting the mixed light signal to said transmission path, and

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and outputs light signals of other wavelengths to said output port.

17. A light branching/inserting apparatus using a wavelength selection filter, said apparatus being connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path, said apparatus comprising:

light branching means for receiving and processing branched light signals for each wavelength;

light inserting means for generating insertion light to be inserted into the light signals on said transmission path,

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from said transmission path is input, an output port from which a light signal to be output to said

transmission path is output, and a branching port connected to said light branching means, and light wave mixing means for mixing insertion light from said light inserting means into light signals output from said output port and outputting the mixed light signal to said transmission path, and

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and outputs light signals of other wavelengths to said output port.

18. An apparatus comprising:

a wavelength selection filter including first, second and third ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the wavelength selection filter branching a respective light from the received WDM light at a wavelength corresponding to a frequency of a surface acoustic wave generated in the wavelength selection filter in accordance with a selection signal applied to the wavelength selection filter, the wavelength selection filter outputting the branched light from the second port and outputting the WDM light having said respective light branched therefrom from the third port; and

a multiplexer multiplexing an insertion light into the WDM light output from the third port, wherein the wavelength selection filter is an acousto-optic tunable filter (AOTF).

19. An apparatus as in claim 18, wherein the insertion light is at the same wavelength as said respective light branched from the WDM light.

20. An apparatus as in claim 18, wherein the WDM light is received by the first port from a transmission path, and the multiplexer outputs the multiplexed insertion light and WDM light to the transmission path.

21. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second and third ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the AOTF branching a respective light from the received WDM light at a wavelength corresponding to a frequency of a surface acoustic wave generated in the AOTF in accordance with a selection signal applied to the AOTF, outputting the branched light from the second port and outputting the WDM light having said respective light branched therefrom from the third port; and

a coupler coupling an insertion light with the WDM light output from the third port.

22. An apparatus as in claim 21, herein the insertion light is at the same wavelength as said respective light branched from the WDM light.

23. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second and third ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the AOTF branching a respective light from the received WDM light at a wavelength corresponding to a frequency of a surface acoustic wave generated in the AOTF in accordance with a selection signal applied to the AOTF, outputting the branched light from the second port and outputting the WDM light having said respective light branched therefrom from the third port; and

means for coupling an insertion light with the WDM light output from the third port.

24. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second and third ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the AOTF branching a respective light from the received WDM light in accordance with a selection signal applied to the AOTF, outputting the branched light from the second port and outputting the WDM light having said respective light branched therefrom from the third port; and

a coupler coupling an insertion light with the WDM light output from the third port.

25. An apparatus as in claim 24, wherein the insertion light is at the same wavelength as said respective light branched from the WDM light.

26. An apparatus comprising:

a wavelength selection filter including first, second, third and fourth ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the second port receiving an insertion light, and, in accordance with a surface acoustic wave generated in the wavelength selection filter via a selection signal applied to the wavelength selection filter, the wavelength selection filter branches a respective light from the received WDM light at a wavelength corresponding to a frequency of the surface acoustic wave, outputs the branched light from the third port and outputs the insertion light and the WDM light having said respective light branched therefrom from the fourth port; and

a monitor monitoring the spectrum of the WDM light before being received at the first port and the spectrum of light output from the fourth port, the monitored spectrums being used to determine whether the wavelength selection filter is operating properly.

27. An apparatus as in claim 26, wherein the wavelength selection filter is an acousto-optic tunable filter (AOTF).

28. An apparatus as in claim 26, wherein the insertion light is at the same wavelength as said respective light branched from the WDM light.

29. An apparatus as in claim 27, wherein the insertion light is at the same wavelength as said respective light branched from the WDM light.

30. An apparatus as in claim 26, wherein the WDM light is received by the first port from a transmission path, and light output from the fourth port is output to the transmission path.

31. An apparatus as in claim 27, wherein the WDM light is received by the first port from a transmission path, and light output from the fourth port is output to the transmission path.

32. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second, third and fourth ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the second port receiving an insertion light, and, in accordance with a surface acoustic wave generated in the AOTF via a selection signal applied to the AOTF, the AOTF branches a respective light from the received WDM light at a wavelength corresponding to a frequency of the surface acoustic wave, outputs the branched light from the third port and outputs the insertion light and the WDM light having said respective light branched therefrom from the fourth port; and

a monitor monitoring the spectrum of the WDM light before being received at the first port and the spectrum of light output from the fourth port, the monitored spectrums being used to determine whether the AOTF is operating properly.

33. An apparatus as in claim 32, wherein the insertion light is at the same wavelength as said respective light branched from the WDM light.

34. An apparatus as in claim 32, wherein the WDM light is received by the first port from a transmission path, and light output from the fourth port is output to the transmission path.

35. An apparatus comprising:

a wavelength selection filter including first, second, third and fourth ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the second port receiving an insertion light, and, in accordance with a surface acoustic wave generated in the wavelength selection filter via a selection signal applied to the wavelength selection filter, the wavelength selection filter branches a respective light from the received WDM light at a wavelength corresponding to a frequency of the surface acoustic wave, outputs the branched light from the third port and outputs the insertion light and the WDM light having said respective light branched therefrom from the fourth port; and

means for monitoring the spectrum of the WDM light before being received at the first port and the spectrum of light output from the fourth port, and for using the monitored spectrums to determine whether the wavelength selection filter is operating properly.

36. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second, third and fourth ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the second port receiving an insertion light, and, in accordance with a surface acoustic wave generated in the AOTF via a selection signal applied to the AOTF, the AOTF branches a respective light from the received WDM light at a wavelength corresponding to a frequency of the surface acoustic wave, outputs the branched light from the third port and outputs the insertion light and the WDM light having said respective light branched therefrom from the fourth port; and

means for monitoring the spectrum of the WDM light before being received at the first port and the spectrum of light output from the fourth port, and for using the monitored spectrums to determine whether the AOTF is operating properly.

37. An apparatus comprising:

an acousto-optic tunable filter (AOTF) including first, second, third and fourth ports, the first port receiving a wavelength divisional multiplexed (WDM) light including a plurality of lights at different wavelengths multiplexed together, the second port receiving an insertion light, and, in accordance with a selection signal applied to the AOTF, the AOTF branches a respective light from the received WDM light, outputs the branched light from the third port and outputs the insertion light and the WDM light having said respective light branched therefrom from the fourth port; and

a monitor monitoring the spectrum of the WDM light before being received at the first port and the spectrum of light output from the fourth port, the monitored spectrums being used to determine whether the AOTF is operating properly.

38. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output,

a branching port connected to said light branching means, and

an insertion port connected to said light inserting means,

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port, and

said light inserting means includes

a light source section for generating light corresponding to all wavelengths which are transmittable on said transmission path,

a light wave mixing/dividing section for wave-dividing the wavelength division multiplexed light in which each light wavelength from said light source section is wave-mixed according to the number of inserted wavelengths and outputting the wavelength division multiplexed light,

an insertion light generating section in which the selected wavelength is variable, which performs modulation for each wavelength division multiplexed light output from said light wave mixing/dividing section and selects and outputs one light wavelength,

a light wave mixing section for mixing a light signal of each wavelength output from said insertion light generating section and outputting the wave-mixed light signals, and

a light amplifying section for amplifying a light signal output from said light wave mixing section and outputting the amplified light signal to the insertion port of said wavelength selection filter.

39. An apparatus according to claim 38, wherein said light inserting means includes

a dispersion compensation section for compensating for the dispersion characteristics of said transmission path, and

a dispersion compensation light amplifying section for compensating for a loss in the light power in said dispersion compensation section.

40. An apparatus according to claim 38, wherein said light inserting means includes a light source control section for sending only a light wavelength which can be inserted, from said light source section to said light wave mixing section.

41. An apparatus according to claim 40, wherein said light inserting means includes an insertion light control section for sending only a light signal of a wavelength to be actually inserted, from said insertion light generating section to said light wave mixing section.

42. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output,

a branching port connected to said light branching means, and

an insertion port connected to said light inserting means,

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port, and

said selection signal has a frequency corresponding to an unused wavelength in the light signal input from said transmission path to remove noise generated in the unused wavelength by said wavelength selection filter.

43. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output,

a branching port connected to said light branching means, and

an insertion port connected to said light inserting means,

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port, and

the apparatus further comprises temperature control means for controlling a device temperature of said wavelength selection filter to be almost constant.

44. A light branching/inserting apparatus using a wavelength selection filter, said apparatus comprising:

branching/inserting means connected to a transmission path through which wavelength division multiplexed light signals are transmitted, which is capable of branching and inserting light signals having at least one wavelength with respect to light signals on said transmission path;

light branching means for receiving and processing light signals branched by said branching/inserting means for each wavelength; and

light inserting means for outputting insertion light to be inserted into the light signals on said transmission path to said branching/inserting means, wherein

said branching/inserting means includes

a wavelength selection filter which can generate a surface acoustic wave of a frequency corresponding to a selection signal, and which has an input port to which a light signal received from the transmission path is input, an output port from which a light signal to be output to the transmission path is output,

a branching port connected to said light branching means, and

an insertion port connected to said light inserting means,

said wavelength selection filter is applied with said selection signal and branches a light signal having a wavelength corresponding to the frequency of said surface acoustic wave contained in the light signal which is sent to said input port from said transmission path and outputs the branched light signal to said branching port, and also inserts insertion light having a wavelength corresponding to the frequency of said surface acoustic wave and which is sent to said insertion port, into the light signal from said transmission path and outputs the light signal to said output port, and

the apparatus further comprises temperature monitoring means for measuring a device temperature of said wavelength selection filter, wherein the frequency of said selection signal is corrected based on measurement results of said temperature monitoring means.