Abstract: A distortion monitor for a non-linear device is provided. The control circuit includes an input coupleable to receive a signal from the non-linear device and a first frequency monitor coupled to the input. The frequency monitor monitors the level of one of even and odd order distortion at a first frequency and creates a first signal indicative of the level of the distortion without the use of a pilot tone.

Abstract: A receiver in an optical network with a bit rate detection circuit for automatically detecting input signal data bit rates to automatically adjust the frequency of a voltage controlled oscillator in the receiver is disclosed. The receiver has a data rate detection and frequency adjustment circuit which automatically detects the data rate of an input signal and automatically adjusts the frequency of the VCO in the receiver in accordance with the data rate of the input signal. The data rate detection and frequency adjustment circuit detects the data rate of the input signal by converting the input signal into a DC voltage value that varies with respect to the data rate of the input signal.

Abstract: A method and apparatus for managing state-of-polarization (SOP) controllers along an optical communications link. When the polarization-mode dispersion (PMD) in the link exceeds a preset limit as determined by a PMD compensator, the SOP controller is directed to change rotation angle in an arbitrary fashion. This shift is only undertaken after other indicators are examined to determine that PMD is the main problem affecting the link, and not simply a consequence of a separate problem that the SOP controller rotation angle should not try to fix. By reducing unnecessary SOP adjustments which can disrupt data traffic, the reliability of the optical link is improved.

Abstract: A method of transmitting a concatenated signal consisting of at least two component signals over an optical network comprising at least three network elements (1, 2, 3, 7, 8, 9, 10) is disclosed in which at least two component signals are transmitted on at least two different wavelengths, and in which the component signals are assigned to the wavelengths for each section between two network elements (1, 2, 3, 7, 8, 9, 10) in such a way as to minimize differential delays between the component signals for a predetermined receiving location. Concatenated transmission capacity can be allocated even if it is no longer available on one wavelength as a coherent whole.

Abstract: A wavelength division multiplexing (WDM) apparatus and a WDM method are disclosed. The apparatus generally comprises an optical interleaver coupled to one or more WDM modules. Two or more interleaver modules may be cascaded together to expand the channel handling capacity. Alternatively, two or more WDM modules may be cascaded together to divide the even and odd channels into subsets. The interleaver interleaves a first signal, containing one or more odd channels and one or more even channels with a second signal, containing a portion of the odd channels and a third signal containing a portion of the even channels. A characteristic frequency spacing between adjacent even channels in the second signal and/or a characteristic spacing between adjacent odd channels in the third signal is about two or more times the value of a characteristic frequency spacing of adjacent channels in the first signal.

Abstract: An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the single-sideband modulated header and data payload propagate through network elements with the same path and the associated delays. The header routing information has sufficiently different characteristics from the data payload so that the signaling header can be detected without being affected by the data payload, and that the signaling header can also be removed without affecting the data payload. The signal routing technique can be overlaid onto the conventional network elements in a modular manner using two types of applique modules. The first type effects header encoding and decoding at the entry and exit points of the data payload into and out of the network; the second type effects header detection at each of~the network elements.

Abstract: The linearity and noise performance of an inexpensive optical signal source are improved using either feedback or feedforward correction techniques. In a feedback embodiment of the invention, a modulation signal, such as a broadband analog CATV signal, is applied to the optical source along with an error signal. The error signal is generated in a feedback path using a high-speed photodiode to detect a portion of the output optical signal generated by the optical source. A delay compensation filter in the feedback path corrects for variations in error signal delay as a function of frequency, such that source nonlinearity and noise may be corrected over a broad bandwidth. In a feedforward embodiment of the invention, an error signal generated from a portion of the output of the optical source is converted to a frequency band outside of the modulation signal bandwidth before being applied to an input of the optical source.

Abstract: A system and method for providing non-blocking routing of optical data through a telecommunications router that allows full utilization of available capacity. The router includes a number of data links that carry optical data packets to and from an optical router. The optical router includes a number of ingress edge units coupled to an optical switch core coupled further to a number of egress edge units. The ingress edge units receive the optical data packets from the data links and aggregate the optical data packets into “super packets” where each super packet is to be routed to a particular destination egress edge unit. The super packets are sent from the ingress edge units to an optical switch fabric within the optical switch core that routes each super packet through the optical switch fabric to the super packet's particular destination egress edge unit in a non-blocking manner (i.e., without contention or data loss through the optical switch fabric).

Abstract: A closed-ring transparent optical communication network that provides for protection of the principal communication channel of each supported wavelength and supports occasional traffic on a separate channel. In the case of a breakdown of or degradation in the principal channel, these communications are redirected to the occasional channel.

Abstract: An optical receiver generates a voltage signal having a predetermined swing from a current signal, and feeds the voltage signal to a decision circuit. An optical receiving element receives the input optical signal, converts the optical signal to a current signal, and provides the current signal to a preamplifier, which converts the input current signal into a voltage signal. The voltage signal is input to an amplifier having a limiting function, which linearly amplifies the voltage signal when the swing of the voltage signal is smaller than a predetermined value, and limitedly amplifies the voltage signal when the voltage signal is greater than the predetermined value. An automatic-gain-control amplifier receives the output from the amplifier with the limiting function, and amplifies the input voltage signal to a voltage signal having a constant swing.

Abstract: As optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and the data payload propagate through network elements with the same path and the associated delays. The header routing information has sufficiently different characteristics from the data payload so that the signaling header can be detected without being affected by the data payload, and that the signaling header can also be removed without affecting the data payload. The signal routing technique can overlaid onto the conventional network elements in a modular manner using two types of applique modules. The first type effects header encoding and decoding at the entry and exit points of the data payload into and out of the network; the second type effects header detection at each of the network elements.

Abstract: In a method of measuring an optical signal-to-noise ratio according to the present invention, a partial optical signal-to-noise ratio is defined, the partial optical signal-to-noise ratio is calculated from a predetermined physical quantity, the sum of inverse numbers of the partial optical signal-to-noise ratios is calculated, and further an inverse number of the sum is calculated to acquire an optical signal-to-noise ratio. The present invention makes it possible to measure optical SNR without directly measuring ASE in the optical signal. The present invention provides a measuring apparatus, a measuring circuit, a pre-emphasis method, an optical communication system, and a controlling apparatus each utilizing this method.

Abstract: In an electronic device, plural circuit boards are plugged into respective connectors, or sockets, in a common backplane circuit board. The backplane maintains the flat circuit boards in fixed relation to one another. Each circuit board is provided with a respective optical transmitter and/or receiver to allow for the transmission of (typically digital) information via a high speed carrier in a light beam through unobstructed free space between the circuit boards. The circuit boards may also be provided with optical splitters and/or combiners as well as apertures to permit light signals to pass through the board's substrate to allow for communication between plural circuit boards. The circuit boards may further include small lenses and/or opaque elements to provide an optical path having selected physical characteristics.

Abstract: A dispersion management system for soliton or soliton-like transmission systems comprises a length of optical fiber (L) in which a plurality of sections (l) made up of components (N,A) of opposite sign dispersions are concatenated together. The duration of the dispersion compensation phase is short in comparison with the propagation interval in the remainder of the system and that the path average dispersion is anomalous.

Abstract: The invention provides a remote control device of an acousto-optic tunable filter, which comprises an acousto-optic tunable filter interpolated in an optical transmission line, capable of controlling an output state of an input light signal by being supplied with a surface acoustic wave control signal through a control port; a surface acoustic wave control signal source to generate the surface acoustic wave control signal, which is provided at a remote place from the acousto-optic tunable filter; and a control unit that receives an information of the surface acoustic wave control signal from the surface acoustic wave control signal source through remote transmission means, and supplies the surface acoustic wave control signal to the control port of the acousto-optic tunable filter.

Abstract: An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator signal are then utilized to enhance the heterodyne signal to noise ratio by removing the intensity noise contributed by the input signal and the local oscillator signal. By measuring portions of the input signal power and the local oscillator signal power and then subtracting out the scaled quantities from the photocurrent measurement during signal processing, the signal to noise of the heterodyne signal is improved beyond that which is accomplished by known balanced receivers.

Abstract: An optical transmitter receiver is provided in which the power of light to be transmitted therefrom is set to a proper value by controlling the relative timing of changing the power of light to be transmitted therefrom. An optical transmitter receiver consists of an optical transmitter, an optical receiver, a signal level detector, and a signal level controller. The optical transmitter transmits a light signal to a mate optical transmitter receiver. The optical receiver receives a light signal from the mate optical transmitter receiver. The signal level detector detects the level of the light signal received by the optical receiver. The signal level controller changes the power of the light signal to be transmitted by the optical transmitter from one value to another according to the signal level detected by the signal level detector.

Abstract: In the method and apparatus for controlling the power level of a laser signal in free space communication, a communication terminal transmits an output laser beam into free space and also receives information, through a channel that is not free space laser based, about the power of the output laser beam measured at a distance and at different times. The terminal determines whether a drop in the power of the output laser beam measured at the distance is due to atmospheric effects based on the received information. The terminal increases the power level of the output laser beam to a desired level if the power drop is determined to be due to atmospheric effects. On the other hand, the terminal lowers the power of the output laser beam to a predetermined level if the power drop is determined to be due to blockage thus avoiding harm to accidental observers that might intrude into the path of the laser beams.

Abstract: A receiver transponder that is implemented in an optical add/drop multiplexer (OADM) is disclosed. The OADM is used in short haul type networks and receives light signals from two opposite directions on input fibers (21, 23). The optical input signals are converted to electrical signals by optical-to-electrical (O/E) converters (51, 53). The output terminals of the converters are connected to an electronic switch (61), which provides protection switching in a protected ring type network. The output signal of the switch can be monitored (65) before the signal enters a reshaping circuit (67), where the signal is reshaped, filtered from a supervisory channel, and adjusted to a proper drive level for a laser (69). The optical signal from the laser can travel a significant distance through a fiber (71) to a client receiver or sustain other forms of attenuation and still have sufficient signal power for reliable detection. An electrical output signal can be provided (73) by the reshaping circuit.

Abstract: A method and apparatus is provided for managing dispersion in a WDM optical transmission system so that transmission performance is improved. The usable optical bandwidth of the transmission system is divided into sub-bands that individually undergo dispersion compensation before being re-combined. Accordingly, in comparison to known dispersion mapping techniques, more WDM data channels reside near a wavelength corresponding to the average zero dispersion wavelength.