Abstract: An apparatus for compensating for optical loss includes a plurality of optical fibers joined to form a plurality of output ports and a fiber junction. A signal amplification device is positioned between the fiber junction and each of the plurality of output ports to communicate with the plurality of optical fibers. An optical transmission signal entering the input port of the apparatus is equally divided at the fiber junction and guided by separate optical fibers toward each of the output ports. Each signal amplification device communicates with the fibers to amplify the optical signals as they pass between the fiber junction and the output ports to compensate for the coupling and other losses experienced by the optical signals due at least in part to the use of the apparatus itself.

Abstract: An apparatus for compensating for optical loss includes at least two optical fibers joined to form a plurality of ports and first and second coupled regions positioned between the ports. Each coupled region includes a signal transmission region adapted to transmit an optical signal. A semiconductor optical amplifier having an active layer is positioned between the first and second coupled regions such that the active layers is substantially aligned with the signal transmission region to provide a pathway for and amplification to an optical signal passed through the apparatus. A method of compensating for optical loss, a loss compensating optical communication system, and a process of manufacturing an optical signal loss compensating device are also disclosed.

Abstract: A modem with nonlinear equalization (100) receives a signal (101) that includes linear and nonlinear distortion. The modem includes a multiplier (107) that frequency shifts the signal to form a baseband signal, which is then sampled by an A/D converter (114) to provide a complex receiver input sample, R(n). A first equalizer (117) equalizes R(n) to form a first equalized result (n). A nonlinear generator (129) forms .vertline.R(n).vertline..sup.2 R(n), which is then equalized by a second equalizer (133) to form a second equalized result (n). A summing device (121) combines the first equalized result (n) with the second equalized result (n) to form a composite equalized result (n). The modem includes a data recovery circuit (125) that determines a received signal point (n) based on the composite equalized result (n) and a predetermined constellation.

Abstract: A modem receiver circuit comprises one or more phase jitter canceling circuits for reducing sinusoidal components of phase jitter in a telecommunications channel. The receiver circuit automatically tracks multiple sinusoidal frequency components and jitter components varying slowly in amplitude and frequency. Each phase jitter canceling circuit is responsive to a phase angle error signal, which is scaled by an adaptive gain constant and appropriately signed. The corrected error signal is passed through a second order loop filter which contains an accumulator with a jitter frequency estimate. The output is integrated into an estimate of the phase of the sinusoidal jitter, which is converted into an estimate of the jitter angle by using a sine lookup table. The resulting estimated jitter component angle is added to the carrier loop phase angle estimate to derive a total receiver phase estimate. The circuit provides rapid acquisition of an accurate initial estimate for the jitter component.