Abstract: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: An apparatus for generating a Carrier-Suppressed Return-to-Zero (CS-RZ) signal is disclosed. The apparatus includes a mixer, a Low Pass Filter (LPF), a driver amplifier and a single external modulator. The mixer generates a modulator input by mixing data with a half clock signal. The LPF band-limits the modulator input data into low frequency band data. The driver amplifier amplifies the modulator input data generated by the mixing of the mixer and the band-limiting of the LPF. The external modulator generates CS-RZ signal, in which the phases of adjacent pulses have been inverted, by applying bias voltage to the modulator input data to be placed at the null point of the transfer function of the external modulator.

Abstract: An adaptive optics system is provided. The system includes a light source, a pair of deformable mirrors and a detection module. The light source is configured to provide an outgoing beam. The outgoing beam has an amplitude and a phase. The first deformable mirror is configured to reflect the outgoing beam and adjust its associated amplitude. The second deformable mirror is configured to reflect the outgoing beam reflected from the first deformable mirror and adjust its associated phase. The detection module is configured to detect an incoming beam and the reflected outgoing beam from the second deformable mirror and generate certain signals. The signals are used to control the first and second deformable mirrors such that the amplitude of the outgoing beam is the same as that of the incoming beam and the phase of the outgoing beam is opposite that of the incoming beam.

Abstract: An optical receiver circuit comprising an optical converter circuit (38), comprising a photodiode and converting optical power into electrical power, a sensor circuit for deriving a control voltage VCONTR as a characteristic value of the electrical power output by the optical converter circuit (38); and an attenuator circuit (44) having a variable attenuation, the attenuation being controlled by the characteristic value of the electrical power output by the sensor circuit so as to obtain a constant output signal level of the optical receiver circuit. An output circuit is also provided and comprises a matching network (46), an amplifier stage (48) and an output transformer (50).

Abstract: The invention provides an optical signal transmitter low in noise and in distortion and provides an optical signal transmission system using this optical signal transmitter. The optical signal transmitter includes a plurality of frequency modulation means for distributing an electric signal into a plurality of electric signals and applying frequency modulation to the distributed electric signals to output and a multiplexing mean for multiplexing a plurality of signals output from the plurality of frequency modulation means and outputting a multiplexed signal. The plurality of frequency modulation means are set to be substantially equal to each other in frequency deviation and in intermediate frequency and to be substantially identical to each other in the phase of each output.

Abstract: Devices and techniques for achieving signal filtering in RF or microwave frequencies by optical filtering using two separate optical paths. Each optical path may include one or more optical resonators to achieve desired optical filtering.

Abstract: A method and apparatus are provided for measuring samples of the electric field of light propagated through a device under test and determining a nonlinear property of the device, such as self-phase modulation or cross phase modulation, using the measured samples.

Abstract: An optical device extracts an information bearing sideband such as an FSK or SCM signal (label) from a composite signal that includes the sideband and an orthogonally modulated signal such as an intensity modulated signal (payload) by employing polarization beam splitting and polarization transformation. Polarization transformation is accomplished by splicing the optical signal into a polarization maintaining fiber at a desired angle so that it is separated into two orthogonal polarizations that experience differential group delay in the fiber. The fiber is characterized by a beat length Lbeat and the fiber is designed to have a length substantially equal to (Lbeat×fc)/2?f, wherein the sidebands of the composite signal are separated by a wavelength difference ?f and fc is the nominal center frequency of the composite signal. This device has been shown to be useful for extracting GMPLS LSC level wavelength labels from either an FSK/IM composite signal or an SCM/IM composite signal.

Abstract: An optical transmitter for sending supervisory data signals and line data signals as a composite optical signal through an optical fiber link is disclosed. The transmitter may take the form of a transmitter, transceiver or transponder and includes circuitry for receiving incoming line data bit rate information for varying and or controlling the modulation index by varying the supervisory carrier frequency amplitude in dependence upon the line data bit rate.

Abstract: An optical-space transmission apparatus for use in communication by using light propagating in a space includes a light-receiving unit, an optical system including a movable mirror and introducing light incident thereon to the light receiving unit with the movable mirror, a controller controlling drive of the movable mirror, and a detecting unit detecting an intensity of the light received in the light-receiving unit. The controller modifies a control characteristic of the movable mirror in accordance with a change in the received-light intensity.

Abstract: This application describes techniques for optical multiplexing and demultiplexing in optical communication systems based on polarization multiplexing of different signal channels.

Abstract: An optical module includes a transmitter optical sub-assembly comprising a transmitter configured to emit a multi-longitudinal-mode (MLM) spectrum signal having an emission spectrum comprising a plurality of distinct narrow-spectrum peaks each corresponding to a longitudinal mode in the transmitter. The emission spectrum can be shifted in wavelength by a change in the transmitter temperature. The optical module also includes a heating and cooling device configured to control the temperature of the transmitter in response to a temperature-control signal and a receiver optical sub-assembly configured to output a pair of differential digital signals in response to an input optical signal.

Abstract: An optical device extracts an information bearing sideband such as an FSK or SCM signal (label) from a composite signal that includes the sideband and an orthogonally modulated signal such as an intensity modulated signal (payload) by splicing the composite signal into a polarization maintaining fiber at a desired angle so that the composite signal is separated into two orthogonal polarizations that experience differential group delay in the fiber. The polarized output signals from the fiber are then coupled to a polarization beam splitter at an equivalent or complementary angle to the desired angle so that one sideband of the composite signal appears at a first output of the beam splitter while another sideband appears at a second output of the beam splitter. The sidebands can then be converted to an electrical data signal by using an appropriate receiver, such as a balanced receiver for FSK signals.