Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-09-24
2002-01-29
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S337000
Reexamination Certificate
active
06342959
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the suppression of transients which can occur in conventional optical wavelength division multiplex (WDM) communication systems.
1. Field of the Invention
It has been shown in J. L. Zyskind et al, “Fast power transients in optically amplified multi-wavelength optical networks”, Optical Fibre Communication conference, vol. 2, OSA Technical Digest Series, PD 31-1, San Jose, 1996, that power transients in chains of highly pumped, deeply saturated erbium doped fibre amplifiers were demonstrated to occur on time scales much faster than those for an individual amplifier. Such fast power transients constitute a major issue for optical networks in which channels are added and dropped either due to network reconfiguration or failures. The surviving channels will suffer error bursts if their powers exceed the dynamic range of the terminal receiver. Protection against such error bursts must be fast enough to limit the surviving channel power excursions.
2. Description of the Related Art
According to a first aspect of the present invention, an optical level controller for a wavelength division multiplexed optical communication network comprises one or more variable gain elements adapted to suppress transient amplitude fluctuations in traffic signals caused by the adding or the dropping of traffic signals at one or more points in the optical communication network, wherein the variable gain element is controlled through a negative feedback loop adapted such that a response time of the negative feedback loop is shorter than the time scale of the transient amplitude fluctuations.
In the present invention, a high speed variable gain element is provided to protect a network from fast power variations.
In one preferred embodiment, the variable gain element is a semiconductor laser amplifier in which the bias of the amplifier is controlled by the negative feed back loop.
In another preferred embodiment, the variable gain element is a Mach-Zehnder optical modulator in which the bias of the modulator is controlled by the negative feedback loop.
Preferably, the negative feedback loop comprises an optical coupler to split a portion of the output of the respective variable gain element onto the negative feedback loop, and a photodiode to detect the split portion of the variable gain element.
Preferably, the negative feedback loop comprises a low pass filter to provide a slowly varying dc voltage for control of the respective variable gain element.
According to a second aspect of the present invention, a wavelength division multiplexed optical communication network comprises a voltage level controller in accordance with the first aspect of the present invention.
The voltage level controller may be provided to condition signals entering a receiving station of the network or alternatively located at an optical cross-connect of the network.
REFERENCES:
patent: 5383046 (1995-01-01), Tomofuji et al.
patent: 5532864 (1996-07-01), Alexander et al.
patent: 5561119 (1996-10-01), Jacquesy et al.
patent: 5739933 (1998-04-01), Dembeck et al.
patent: 5907420 (1999-05-01), Chraplyvy et al.
patent: 5923462 (1999-07-01), Haxell et al.
patent: 6091535 (2000-07-01), Satoh
patent: 0 305 995 (1989-03-01), None
patent: 0 792 035 (1997-09-01), None
Inoue, K., et al., “Tunable Gain Equalization Using a Mach-Zehnder Optical Filter in Multistage Fiber Amplifiers,”IEEE Photonics Technology Letters, 3 (1991) August, No. 8, New York, US.
Srivastava, A., et al., “Fast Gain Control in an Erbium-Doped Fiber Amplifier”,osa tops On Optical Amplifiers and Their Applications, 1996, vol. 5, 1996 OAA Program Committee (eds., 1996 Optical Society of America.
Srivastava, A., et al., “Fast-Link Control Protection of Surviving Channels in Multiwavelength Optical Networks,”IEEE Photonics Technology Letters, vol. 9, No. 12, December 1997.
Haxell Ian
Simeonidou Dimitra
Alcatel
Negash Kinfe-Michael
LandOfFree
Transient suppression in an optical wavelength division... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transient suppression in an optical wavelength division..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transient suppression in an optical wavelength division... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2852787