Optical: systems and elements – Optical amplifier – Optical fiber
Reexamination Certificate
1998-01-04
2001-02-13
Hellner, Mark (Department: 3662)
Optical: systems and elements
Optical amplifier
Optical fiber
C359S199200, C385S017000
Reexamination Certificate
active
06188509
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a bidirectional add/drop amplifier module, more specifically, to the bidirectional add/drop amplifier module that is simply constructed using a single bidirectional multiplexer such as an arrayed-waveguide grating.
This invention may be more clearly understood by referring to the cited papers, as follows:
F. Elrefaie, “Multiwavelength survivable ring network architectures”,
International Conference on Communication,
1993, paper 48.7; F. Shehadeh, R. S. Vodhanel, M. Krain, C. Gibbons, R. E. Wagner, and M. Ali, “Gain-equalized, eight-wavelength WDM optical add-drop multiplexer with an 8-dB dynamic range”,
IEEE Photonics Technol. Lett.,
vol. 7, no. 9, pp. 1075-1077, September, 1995; K. P. Ho, S. K. Liaw , and C. Lin, “Performance of an eight-wavelength bidirectional WDM add/drop multiplexer with 80-Gbit/s capacity”,
Optical Fiber Communication
'
97
, paper TuR1; J. L. Gimlett, and N. K. Cheung, “Effects of phase-to-intensity noise conversion by multiple reflections on gigabit-per-second DFB laser transmission systems”,
J. Lightwave Technol.,
vol. 7, no. 6, pp. 888-895, June, 1989; N. Henmi, Y. Aoki, S. Fujita, Y. Sunohara, and M. Shikada, “Rayleigh scattering influence on performance of 10 Gb/s optical receiver with Er-doped optical fiber preamplifier,”
IEEE Photonics Technol. Lett.,
vol. 2, no. 4, pp. 277-278, April, 1990; C. Barnard, J. Chrostowski, and M. Kavehrad, “Bidirectional fiber amplifiers,”
IEEE Photonics Technol. Lett.,
vol. 4, no. 8, pp. 911-913, August, 1992; K. Kannan, and S. Frisken, “Unrepeatered bidirectional transmission system overa single fiber using optical fiber amplifiers,”
IEEE Photonics Technol. Lett.,
vol. 5, no. 1, pp. 76-79, January, 1993; W. Y. Guo, and Y. K. Chen, “High-speed bidirectional four-channel optical FDM-NCFSK transmission using an Er
3+
-doped fiber amplifier,”
IEEE Photonics Technol. Lett.,
vol. 5, no. 2, pp. 232-235, February, 1993; Y. H. Cheng, N. Kagi, A. Oyobe, and K. Nakamura, “622 Mb/s, 144 km transmission using a bidirectional fiber amplifier repeater,”
IEEE Photonics Technol. Lett.,
vol. 5, no. 3, pp. 356-358, March, 1993; R. J. Orazi, and M. N. McLandrich, “Bidirectional transmission at 1.55 microns using fused fiber narrow channel wavelength division multiplexers and erbium-doped fiber amplifier,”
IEEE Photonics Technol. Lett.,
vol. 6, no. 4, pp. 571-574, April, 1994; M. O. van Deventer, and O. J. Koning, “Unimpaired transmission through a bidirectional erbium-doped fiber amplifier near lasing threshold,”
IEEE Photonics Technol. Lett., vol.
7, no. 9, pp. 1078-1080, September, 1995M.; O. van Deventer, and O. J. Koning, “Bidirectional transmission using an erbium-doped fiber amplifier without optical isolators,”
IEEE Photonics Technol. Lett.,
vol. 7, no. 11, pp. 1372-1374, November, 1995.
A wavelength division multiplexing (WDM) optical network uses different wavelengths to transmit a plurality of optical signals unconcernedly with any transmission mode and speed, whereby a super highway and wide area network can be realized. The network requires a drop function for receiving a wanted signal at each node and an add function for transmitting a wanted signal at each node. Therefore, a WDM add/drop multiplexer is an important constituent for constructing the WDM optical network. The add/drop multiplexer is especially emphasized in a WDM ring network.
In order to a bidirectional ring network using a unidirectional WDM add/drop multiplexer, at least two pairs of optical fiber are required. A bidirectional WDM add/drop multiplexer that can not only transmit but also add/drop a signal in bidirection is significantly reduce consumption of the optical fiber required in constructing the bidirectional ring network.
Such bidirectional WDM add/drop multiplexers are proposed in U.S. Pat. No. 5,548,438 issued Apr. 20, 1996 and entitled “Bidirectional optical amplifier”, U.S. Pat. No. 5,633,741 issued May 27, 1997 and entitled “Multichannel optical fiber communications”, and a paper of K. P. Ho, et al., “Performance of an eight-wavelength bidirectional WDM add/drop multiplexer with 80-Gbit capacity”, Proceeding of Optical Fiber Communication, 1997.
These bidirectional WDM add/drop multiplexers, however, use a 1×N demultiplexer and an N×1 multiplexer, whereby their structures are very complicated and the manufacturing cost is very high.
SUMMARY OF INVENTION
This invention is aimed to obtain a bidirectional WDM add/drop amplifier module simply and inexpensively manufactured using a single N×N multiplexer.
The bidirectional WDM add/drop amplifier module according to this invention comprises bidirectional signal add/drop means using a single N×N multiplexer, and bidirectional signal amplifying means connected to the signal add/drop means in series.
The N×N multiplexer has a channel structure that comprises, at each side, a wavelength division multiplexed signal (WDMS) input end, a WDMS output end, at least two separated signal input ends, and at least two separated signal output ends. At least one of the separated signal input ends is designated as an added signal input end, while at least one of the separated signal output ends is designated as a dropped signal output end. The separated signal output ends except for the dropped signal output end are connected to the signal input ends at the same side.
The number of the separated signal output ends is preferably equaled to the number of the separated signal input ends, while the number of the separated signal input ends is preferably equaled to the number of the separated signal output ends.
According to the invention, the WDM add/drop amplifier module further comprises signal separating means provided at both ends of the bidirectional signal add/drop means to distinguish paths of different WDMSs and to transmit through each path respectively.
Preferably, a unidirectional optical band pass filter is provided between the WDMS output end of the N×N multiplexer and the signal separating means to eliminate a relative intensity noise.
The bidirectional signal amplifying means may be selected from a group of amplifiers consisting of an erbium doped fiber amplifier, praseodymium doped fiber amplifier and semiconductor optical amplifier, and assigned one by one end of the bidirectional signal add/drop means.
The N×N multiplexer may be an arrayed-waveguide grating.
A difference between the frequency of the added signal and the frequency of the dropped signal is preferred to be set into an amount of the free-spectral range of the arrayed-waveguide grating multiplied by integer comprising zero.
According to this invention, there is also provided a bidirectional signal add/drop apparatus for transmitting WDMS in bidirection and adding/dropping a signal using a single N×N multiplexer.
Other advantages and features of the present invention will become apparent from the following description, including the drawings and claims.
REFERENCES:
patent: 5633741 (1997-05-01), Giles
patent: 5740289 (1998-04-01), Glance
patent: 5801879 (1998-09-01), Burton et al.
patent: 5926590 (1999-07-01), Mao
patent: 5995259 (1999-11-01), Meli et al.
patent: WO 99/65164 (1999-12-01), None
Chung Yun Chur
Kim Chul Han
Lee Chang Hee
Akin Gump Strauss Hauer & Feld L.L.P.
Hellner Mark
Korea Advanced Institute Science and Technology
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