Abstract: An optical transponder/transceiver for intermediate range (e.g., 10-50 km) optical communication applications utilizes an electroabsorption modulated laser for the transmitting device. Preferably, the laser operations at a wavelength of approximately 1310 nm and comprises an electroabsorption modulated Fabry-Perot laser.

Abstract: A unique sensor is used to detect a transmission impairment that may have affected incoming optical channel signals. The sensor, more specifically, selects a group of the incoming channel signals and generates a first power signal, P0, over the selected group of signals and generates a second power signals, P1, over a weighted version of the selected group of channel signals. The sensor then generates, as a function of the first and second power signals, P0 and P1, a signal indicative of whether the particular transmission impairment affected the levels of individual ones of the incoming channel signals. If so, then control apparatus offsets the impairment accordingly.

Abstract: An apparatus and method for detecting a signal in an optical data network is disclosed. A peak power level and an average power level are measured for an optical input to an optical detector. A threshold power level is associated with each average power level that is sufficient to distinguish a data signal form optical noise at the average power level. A signal is detected if the measured peak power level exceeds the threshold power level appropriate for the average power level. In one embodiment, a threshold value of a ratio of the peak power level to the average power level is calculated and a signal is detected if the ratio of the measured peak power level to the average power exceeds the threshold value.

Abstract: The present invention provides an improved full-duplex optical communications system. The system includes: at least one office, where the at least one office provides a plurality of channels, the plurality of channels comprising a plurality of signal channels and a plurality of continuous wave (CW) channels; at least one optical add/drop multiplexer (OADM) optically coupled to the at least one office; and a subscriber premises optically coupled to the at least one OADM, where at least one of the plurality of signal channels and at least one of the plurality of CW channels are dropped from the plurality of channels to the subscriber premises by the at least one OADM, where the subscriber premises modulates the dropped at least one of the plurality of CW channels, where the modulated at least one of the plurality of CW channels is added to the plurality of channels by the at least one OADM.

Abstract: Methods and apparatus for multiplexing and demultiplexing optical signals. An interleaver having a modified Mach-Zehnder interferometer as a first stage is used as a wavelength division multiplexer. This first stage is combined with one or more cascaded stages, each having a beam splitter and an optical delay element. A light beam including a number of signals at different wavelengths is received. The beam is split such that approximately half of each signal is contained in one of two sub-beams. One of the two sub-beams passes through a delay element, which provides a phase shift. The two sub-beams are recombined and split again. Each wavelength adds constructively or destructively in the new sub-beams such that the signals are separated—some wavelengths are in one of the new sub-beams, some are in the other. One of these sub-beams is delayed, and the two are combined and split again, improving the separation.

Abstract: A system which improves wavelength tolerance, compensates dispersion in a simple way, reduces limitation of the fiber input power is disclosed. The operation includes receiving a clock signal from a system clock source; modulating a single mode optical signal based on the clock signal and generating an optical pulse signal having two longitudinal modes, the frequency interval thereof being n×B, n being a natural number and B being a transmission speed; generating a partial response signal by converting a binary NRZ signal from a digital signal source in synchronism with the system clock source; and modulating the optical pulse signal based on the partial response signal, and outputting a binary RZ modulated signal. The binary RZ modulated signal is input into a receiver, where two partial response components in the optical spectra of the input signal are divided, and one or both of the components are received.

Abstract: An optical ring is provided for propagating optical signal pairs over wavelength connections between nodes. Each optical signal pair includes two signals at different wavelengths. At one or more of the nodes, one signal of the pair acts as a transmit signal and the other acts as a receive signal. If a failure is detected the optical signal pair is redirected over a protection path without changing the wavelengths of the transmit and receive signals. This may be achieved by reversing a propagation direction for each of the signals comprised by the redirected optical signal pair.

Abstract: In a method and system for evaluating distributed gain in an optical transmission system, a data signal and a residual pump laser signal propagating in opposite directions within a waveguide are monitored. Modulation of the residual pump laser signal is correlated with low frequency components of the data signal. This correlation is used to determine cross-talk between the data signal pump laser signals, as a function of location within the waveguide. The distributed gain is then evaluated from the cross-talk, using a known relationship, or proportionality, between gain and cross-talk.

Abstract: Optical infinite impulse response (IIR) filters are efficient polarization mode dispersion (PMD) compensators, requiring fewer stages than finite impulse response (FIR) filters. IIR filter architectures incorporating allpass filters allow the phase and magnitude compensation to be addressed separately. An IIR filter PMD compensator comprising a polarization beam splitter, allpass filters, polarization rotation devices, a 2×2 filter, and a polarization beam combiner optically coupled is described.

Abstract: A method and device for optical add/drop is disclosed. The add/drop splits an input signal into two portions. The first portion is optically filtered to remove the channels, leaving an unmodulated carrier which is modulated with the newly added information. The second portion is split again into the through channels and a channel to be dropped. The dropped channel is detected or terminated and the through channels are recombined with the newly added channel to form an output optical signal. If desired, multiple channels may be dropped at the add/drop node. A dense wavelength division multiplexed (DWDM) optical communication system incorporating the add/drop node is also disclosed.

Abstract: An optical fiber (12a) with a large effective core area and a large chromatic dispersion value is disposed on an input side of signal light, and an optical fiber (12b) with a small effective core area and a small chromatic dispersion value or a chromatic dispersion value of negative polarity is disposed on an output side of the signal light. A pumping light source (14) generates pumping light of 1450 nm to cause Raman amplification of 1550 nm in the optical fiber (12b). The output light from the pumping light source (14) enters the optical fiber (12b) from the back through a WDM optical coupler (16). Provided that y=(Pin−&agr;)/(Pp·10 Log L) where input power of the optical fiber (12a) (i.e.

Abstract: Disclosed herein is an optical cross-connect device including first wavelength demultiplexing sections each for demultiplexing WDM (wavelength division multiplexed) signal light into a plurality of optical signals, wavelength group generating sections each for receiving the optical signals from each first wavelength demultiplexing section to generate wavelength groups, first wavelength multiplexing sections each for receiving each wavelength group from each wavelength group generating section to output a WDM wavelength group, a routing section for routing the input WDM wavelength groups, second wavelength demultiplexing sections each for receiving each WDM wavelength group from the routing section to output a wavelength group having a plurality of wavelengths, wavelength converting sections each for performing wavelength conversion of each optical signal of the wavelength group output from each second wavelength demultiplexing section, and second wavelength multiplexing sections each for wavelength division m

Abstract: An optical communications system employs a plurality of optical nodes interconnected in a ring configuration by at least two optical transmission media, for example, optical fiber. The at least two optical transmission media, in this example, provide optical service transmission capacity and optical protection transmission capacity. Efficient restoration of optical communications between optical nodes in the ring, after an optical transmission media failure, is realized by employing a relatively simple and efficient optical switch matrix having a first number of possible switching states and, then, by utilizing only a second number of the switching states fewer than the first number to switch optically from the optical service transmission capacity of the failed or faulted optical transmission media to the optical protection transmission capacity of another optical transmission media.

Abstract: A method and apparatus is provided for transmitting an optical signal through an optical fiber. The apparatus includes an optical signal source, which generates an optical signal having a plurality of optical channels onto which data is modulated. Each of the optical channels is defined by a different carrier wavelength. A phase modulator imparts phase modulation to the plurality of optical channels so that channels nearest a zero dispersion wavelength of the optical fiber are more closely spaced to one another than channels farthest in wavelength from the zero dispersion wavelength of the optical fiber.

Abstract: An optical time-division multiplexing transmitter module which includes an optical circulator, an optical coupler which splits in two an optical signal in the form of a pulse beam output from the circulator, first and second double-pass electro-absorption (DPEA) modulators positioned respectively to receive and modulate one and the other of the two split signals, and reflect the modulated signals back through the coupler to the circulator. The coupler multiplexes the reflected signals and directs the multiplexed signals to the circulator which then guides them to exit through a circulator output port. An optical delay circuit is positioned between in the path of one of the split signals so as to delay it relative to the other.

Abstract: The invention relates to an optical add/drop device comprising at least two optical filter units (OADE). An individual filter unit comprises a first, second and third port so that when all signals of the aggregate signal are present at the first port (A), said desired signal is present at the second port (B) and all other signals except the desired signal are present at the third port (C). To provide flexible altering possibilities, a number of filter units (OADDE . . . OADE) are placed in succession to form at least two pairs of filter units in such a way that in each pair the first filter unit operates at a given wavelength as a signal dropping unit and the second as an adding unit corresponding to the first unit, adding to the aggregate signal a signal having the same wavelength.

Abstract: An optical device protection system provides dedicated and shared protection for a plurality of optical working devices which may include four-port optical working devices. The system includes an optical switch structure for routing an optical signal around an optical device when the optical device exhibits an error condition. A protection optical device performs a desired operation on the optical signal, wherein the optical switch structure directs the optical signal through the protection optical device. The use of liquid crystal switches allows the optical switch structure to sense an incorrect capacitance value associated with the liquid crystal switch. A control signal is then generated in response to the incorrect capacitance value. Thus, the optical device protection system provides flexibility and a low cost method for protecting complex optical devices.

Abstract: An optical transmitter includes a directly modulated semiconductor laser and a non-linear optical intensity modulator which is connected in series with the output of the laser. High frequency analogue modulating signals are applied both to the laser and to the modulator. The modulator has a transfer characteristic such that it cancels intermodulation distortion in the output from the laser, to give a source with an improved dynamic range. The transmitter is suitable for use in an analogue optical distribution system for cellular radio.

Abstract: A testing device performs testing on a multistage multi-branch optical network, which contains optical lines (such as optical fibers) that are connected together at connection points (e.g., optical couplers) in a multistage multi-branch manner. An OTDR measurement device uses software to perform fault determination with respect to the multistage multi-branch optical network. Herein, optical pulses are input to an input end of the multistage multi-branch optical network, wherein they are reflected at certain portions of the optical lines and the connection points while propagating through the optical lines. Then, reflected beams are returned to the input end and are mixed together as response light, which is measured by the OTDR measurement device. The response light is converted to a plurality of digital waveform data representing a measured waveform, which is then divided into multiple ranges on the basis of the Fresnel reflection points and connection points.

Abstract: Temperature compensation of a wavelength-division-multiplexed (WDM) passive optical network (PON) communication system uses power measurements from each of it remote nodes (RNs) to adjust the frequency of an associated multifrequency laser (MFL). Changes in the power level at each RN caused by frequency drift of its waveguide grating router (WGR), due to changes in the WGR temperature, is determined by monitoring the power level received at each RN and corrected by appropriate changes in the temperature of the associated MFL. The WGR uses one output port (e.g., channel 1) which is looped-back through the WGR a second time to increase the temperature sensitivity of the power measurements. A temperature-control algorithm controls the temperature of the MFL as a function of changes in the received power at the WGR.