Abstract: A polarization scrambler unit includes a plurality of polarization scramblers, a switching unit for coupling one of the polarization scramblers to a transmission line fiber, a detection unit for detecting an output signal from the polarization scrambler coupled to the transmission line fiber, and a controlling unit for switching, via the switching unit, between the polarization scramblers and another polarization scrambler whenever a false output signal is detected by the detection unit. Thus, the polarization scrambler unit has a redundant structure.

Abstract: An optical communication system and a communication network are disclosed herein capable of transmitting optical signals with high optical launch power over long distances with suppression of stimulated Brillouin scattering. A method of transmitting optical signals is also disclosed herein which comprises transmitting optical signals at high optical launch power with a high carrier-to-noise ratio (CNR). Passive optical networks disclosed herein provide greater reach and/or increased splits.

Abstract: The present invention provides an optical wavelength multiplexing transmission apparatus and an optical output control method for an optical wavelength multiplexing transmission apparatus in an optical wavelength multiplexing transmission system using a main signal light and an OSC light. The optical wavelength multiplexing transmission apparatus (10a) is made up of a first transmitting/receiving section (52a), a second transmitting/receiving section (52b) and an apparatus supervisory control unit (54). This can not only achieve quick restoration from troubles, but also stably calculate an optical output level even if a change of the number of wavelengths to be multiplexed takes place in a main signal light, and even save troublesome adjustments for the improvement of reliability of a transmission line while eliminating the need for a signal source for the adjustment of a receive optical level at the initial installation.

Abstract: A supervisory system and supervisory method of an optical amplifier repeater are proposed that can implement operation supervision taking account of the characteristics of individual supervisory targets of the optical amplifier repeater, thereby achieving higher reliability.

Abstract: A method and apparatus are disclosed for terminating optical links in an opticalnetwork based on performance requirements. The present invention forces the termination of the received optical signals at each node only on the protection ring and does not force termination on the working ring, unless necessary to satisfy performance requirements. A signal on an end-to-end light path on the working ring is terminated only when required by engineering rules, such as signal-to-noise requirements. Specifically, the present invention does not force terminate an end-to-end light path on the working ring at a given node (or on a link between two nodes) unless the signal will fail to meet certain criteria, such as a minimum optical signal-to-noise ratio, at the next node.