Optical: systems and elements – Optical amplifier – Optical fiber
Reexamination Certificate
1998-04-28
2001-11-13
Moskowitz, Nelson (Department: 3662)
Optical: systems and elements
Optical amplifier
Optical fiber
C359S199200, C385S012000
Reexamination Certificate
active
06317255
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to lightwave communication systems and, more particularly, to techniques for controlling the power level of an optical signal so that harm from the optical signal emanating at a downstream fault in an optical fiber path is substantially reduced.
BACKGROUND OF THE INVENTION
Retinal and other types of eye injury can occur from inadvertent direct exposure to the optical signals used in present communication systems. Danger is presented by the power and the wavelength of such signals. Generally, these systems operate with signals having relatively high power concentrated in a tiny beam located outside the visible region.
Recent developments in optical networking have only heightened existing safety concerns. For example, optical amplifiers and other optical components are now being developed to drive optical signals to even higher output power levels. Multi-wavelength systems are also a concern because the total optical power in the optical fiber is the sum of the powers of the individual wavelength components. Consequently, optical systems having total output power of 20 dBm or more are now being realized as a result of advances in optical amplifier and multi-wavelength optical networking technologies.
Because the extent of injury is most likely proportional to the total output power and the time of exposure, it is necessary to quickly shut off or reduce the output power of a network element in the event of a fiber cut, removed connector, or any other discontinuity in the optical path. In prior arrangements, control of upstream elements relies entirely upon downstream elements nearer to the fault. For example, downstream network elements perform fault detection and localization by monitoring the degradation or interruption of the forward propagating signal, i.e., the signal propagating downstream. If such a degradation or interruption is detected, the network control and management system then communicates the necessary supervisory signals to switch off the upstream network element. This scheme is limited in several ways. First, the scheme will only work for faults that occur between the upstream and downstream elements. Secondly, this scheme will fail if, by virtue of the system failure, the downstream element cannot communicate with the upstream element, e.g., if the supervisory channel is lost as a result of the discontinuity in the optical path. Even if this scheme works, there are other issues of added cost and complexity for such control and the possibility of delay in effecting control.
SUMMARY OF THE INVENTION
Automatic reduction of optical signal power supplied by an upstream network element by a prescribed amount is achieved without the use of downstream control elements by using reflected optical signal power that is generated within the optical fiber path as a result of a downstream fiber cut, open connector, or other potentially hazardous discontinuity. Upon capturing and processing the reflected optical signal power at an upstream position in the optical fiber path, the optical signal power supplied by the upstream network element is automatically reduced. The optical signal power may either be reduced by an amount that is a function of the measured reflected optical signal power or may be completely shut off until the faulty condition is resolved. By using reflected optical signal power within the optical transmission path, the present invention does not require any additional signaling from downstream network elements or from the network control and management system and avoids delay.
In one illustrative embodiment, control circuitry is located at an upstream position to capture and process the reflected optical signal that is generated as a result of the downstream fault. The control circuitry may be coupled to a network element, such as a fiber optical amplifier, to control the output power level of the network element in response to the downstream fault. More specifically, the control circuitry generates a control signal and supplies this control signal to the network element to reduce the output power level of the network element accordingly. Alternatively, upon processing the reflected optical signal, the control circuitry may be used to introduce a predetermined amount of loss into the optical fiber to reduce the optical signal power below harmful levels. The control circuitry may be analog, digital, or may be implemented using a microprocessor under software or firmware program control.
REFERENCES:
patent: 4911515 (1990-03-01), So et al.
patent: 5218608 (1993-06-01), Aoki
patent: 5355250 (1994-10-01), Grasso et al.
patent: 5475521 (1995-12-01), Heiemann
patent: 5504617 (1996-04-01), Spirit
patent: 5664131 (1997-09-01), Sugiya
patent: 5680246 (1997-10-01), Takahashi et al.
patent: 5812710 (1998-09-01), Sugaya
patent: 5818629 (1998-10-01), Kinoshita
patent: 2304452 (1997-03-01), None
patent: 5-291667 (1993-11-01), None
patent: 07015055 (1995-01-01), None
Sato et al, IEEE Photonics Tech. Letters, vol. 3, #11, Nov. 1991 pp. 1001-1003;Abst. Only Herewith.*
Sugaya et al, OAA '95,paper Fc3, pp 3-6, Jun. 16, 1995.*
Nakagawa et al, Bit Rate Flexible Transmission Field Trial . . . , NTT Transmission System Labs, PDP11-1; pp. 341-343, Oct. 1995.*
U.S. patent application Ser. No. 08/932,679, filed on Sep. 18, 1997 entitled “Optical Transmission Line Automatic Power Shut-down System” by Vibha Prakash Goel et al.
Fatehi Mohammad Taghi
Nelson Bruce Lee
Raychaudhuri Kamal Kumar
Lucent Technologies - Inc.
Moskowitz Nelson
Murgia Gregory J.
LandOfFree
Method and apparatus for controlling optical signal power in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for controlling optical signal power in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling optical signal power in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2572280