| US 7,509,055 B2 | ||
| Optical transmission system with automatic signal level adjustment and startup functions | ||
| Hiroaki Tomofuji, Kawasaki (Japan); Takuji Maeda, Kawasaki (Japan); Taizo Maeda, Kawasaki (Japan); Hideki Kobayashi, Yokohama (Japan); Tatsuo Nagayoshi, Yokohama (Japan); and Tetsuo Wada, Kawasaki (Japan) | ||
| Assigned to Fujitsu Limited, Kawasaki (Japan) | ||
| Filed on Jan. 11, 2008, as Appl. No. 12/7,591. | ||
| Application 12/007591 is a continuation of application No. 10/898541, filed on Jul. 26, 2004, granted, now 7,343,102. | ||
| Claims priority of application No. 2004-007857 (JP), filed on Jan. 15, 2004. | ||
| Prior Publication US 2008/0159753 A1, Jul. 03, 2008 | ||
| Int. Cl. H04B 10/00 (2006.01) | ||
| U.S. Cl. 398—160 | 2 Claims |
| 1. An optical transmission system for transporting optical signals, comprising:
(a) a first optical transmission device that measures an output power level of supervisory control channel signals being transmitted
and sends out a downstream message containing the measured output power level; and
(b) a second optical transmission device disposed downstream with respect to the first optical transmission device, comprising:
an optical transmission unit comprising an optical amplifier unit to boost optical signals and a variable optical attenuator
to attenuate the optical signals, and
a controller that receives the measured output power level from the first optical transmission device, monitors an input power
level of the supervisory control channel signals at the input of the optical amplifier unit, estimates section loss of main
optical signals between the first and second optical transmission devices based on the received output power level and the
monitored input power level, determines a required attenuation of the variable optical attenuator from the estimated section
loss, adjusts the variable optical attenuator accordingly, and selects and sets operating mode of the optical amplifier unit;
wherein the controller activates the optical amplifier unit in AGC mode with a gain calculated from the estimated section
loss, and sets the optical amplifier unit to operate in ALC mode with an appropriate output power level according to the number
of incoming wavelengths, when the supervisory control channel signals indicating transmission of main signals are received.
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