Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

Agere Systems Inc.

Triquint Technology Holding Co.

Yong-Kwan Park

Kyeong-Soo Kim

Reed K Even

Song Jiang

Fengkun Liu

Peter Van Eijk

Woojune Kim

Piet Van Heyningen

John David Weld

Jonathan A Nagel

Daniel A Fishman

Venkataraman Swaminathan

Naresh Chand

Thomas H Daugherty

Gerard Edmond Henein

Kinichiro Ogawa

Piet Van Hevingen

Felix C Anigbo

Ming-Lai Kao

Anpei Pan

Moon Soo Park

Wouterus Muys

An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit via a working optical fiber, (2) a protection OSU of a protection circuit via a protection optical fiber, and (3) one or more optical network terminals (ONTs). The present invention enables fast protection switching from the working OSU to the protection OSU. In one embodiment, the arrival times of corresponding upstream ranging reply PLOAM cells are measured at both the working and protection OSUs during ranging operations of the working OSU. In another embodiment, a cell delineation procedure is initiated at the protection OSU during normal, non-ranging operations of the working OSU to enable the protection OSU to correctly delineate upstream cells and the arrival times of corresponding upstream cells are then measured at both the working and protection OSUs. In either case, a propagation delay value is generated based on the measured arrival times for use by the protection OSU for communications with the one or more ONTs if and when protection switching is implemented upon detection of a failure in the working circuit, possibly without requiring the protection OSU to perform any ranging for the one or more ONTs.

Fast protection switching by snooping on upstream signals in an optical network

An apparatus for wavelength multiplexing optical signals, wherein the apparatus includes at least one optically conductive sleeve, at least one collimating lens positioned to receive a optical signal from the at least one sleeve, and at least one dichroic splitter positioned to receive the optical signal from the at least one collimating lens. A filter may further be positioned to receive the optical signal from the at least one dichroic splitter in order to further filter the optical signal. The apparatus for wavelength multiplexing is configured to provide optical isolation of at least 75 dB via the combination of the at least one dichroic splitter and filter elements.

Apparatus and method for transmitting optical signals through a single fiber optical network

An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit via a working optical fiber, (2) a protection OSU of a protection circuit via a protection optical fiber, and (3) one or more optical network terminals (ONTs), where the protection OSU has a protection burst mode receiver (BMR) configured to receive an upstream optical signal from the optical splitter. The algorithm determines whether the protection OSU is functioning improperly. A reset pulse is applied at the protection BMR at a particular timing position and an attempt is made to interpret the current upstream cell received at the protection BMR. This process is repeated using different timing positions for the BMR reset pulse until the current upstream cell is correctly interpreted, e.g., based on the correct identification of an ATM header error correction (HEC) byte in the upstream cell. If, after a specified number of cycles, no upstream cells are correctly interpreted, then the protection circuit is determined to have failed. In one embodiment, the algorithm is based on a cell delineation procedure implemented as a state machine.

Health check algorithm for protection circuit in optical network

An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit, (2) a protection OSU of a protection circuit, and (3) one or more optical network terminals (ONTs), where an ONT has (i) a working line termination (LT) unit of the working circuit and connected to the optical splitter via a working optical fiber and (ii) a protection LT unit of the protection circuit and connected to the optical splitter via a protection optical fiber. The present invention enables fast protection switching from the working circuit to the protection circuit. The arrival times of corresponding downstream cells are measured at both the working and protection LT units of the ONT, and information related to the arrival times is transmitted from the ONT to the protection OSU. A propagation delay value is generated based on the transmitted information for use by the protection OSU for communications with the ONT if and when protection switching is implemented upon detection of a failure in the working circuit.

Fast protection switching by snooping on downstream signals in an optical network

This invention is a new communication system in which multichannel broadcast digital services are distributed to each user with the broadcast services signal riding in the passband above a digital baseband signal. The system can deliver more than 1 Gbps additional bandwidth to each subscriber. The passband bandwidth will accommodate growth in downstream services including video on demand, higher speed web downloads including improved streaming audio and video, HDTV, interactive video, and personalized video. The invention requires only a single fiber path and a single optical receiver for each user or group of users. A single fiber, single optical receiver system is much less expensive than two systems, one transmitting baseband and the other passband. A single receiver is greatly cost beneficial to achieving economical fiber to the home.

Optical communication system optically combining both baseband and passband signals

A method of determining Inter-Symbol Interference (ISI) in transmission systems first measures, for each of a plurality of received signal having different Signal-to-Noise (S/N) ratio, the minimum Bit-Error Rate (BER) as a function of the threshold level of a decision circuit at the system receiver. The measurements are then repeated on the system or on a simulated system where one or more segments of the transmission facility has been replaced with one or more non-ISI producing attenuators. The ISI levels for a given BER value is determined from the first and second sets of measurements. An alternate method measures minimum BER values of the system and the simulated system, as a function of the received signal power, for received signals having different S/N ratios. The ISI levels for a given BER value is then determined from these two sets of measurements.

Method of determining inter-symbol interference in transmission systems

At least one dispersion compensating fiber (DCF) is utilized to compensate for chromatic dispersion of an externally modulated signal carried by at least one single mode, standard fiber optic cable. The self phase modulation (SPM) effect in the standard fiber is characterized by a pulse compression and associated pulse distortion when a 1550 nm wavelength signal is launched into the fiber. Because the SPM effect in the DCF fiber is characterized by a pulse broadening for the same signal, the DCF fiber is also utilized to compensate for the SPM effect in the standard fiber. To this end, the signal power launched into the DCF fiber is controlled such that precise compensation for the SPM effect in the standard fiber can be achieved. Control of the launching power is needed because the mode field diameter of the DCF fiber is smaller than that of the standard single mode fiber so that the DCF fiber experiences the SPM effect at a lower power than the single mode fiber.

System and method for simultaneously compensating for chromatic

A technique for reducing the power threshold at which stimulated brillouin scattering ('SBS') occurs within an optical fiber by directly modulating a conventional laser generating an optical signal propagated along that fiber. The modulation is accomplished by employing an alternating waveform to induce a dither upon the laser output. The specific frequency of the alternating waveform is chosen to be very much lower than the low frequency cut-off of any receiver coupled to the optical fiber, but sufficiently high enough to efficiently suppress the Brillouin gain. This dithering causes the laser to be frequency modulated, thereby broadening the effective linewidth of the laser output and increasing the SBS power threshold.

Reduction of stimulated brillouin scattering in a fiber optic

An externally modulated laser-based transmitter is disclosed which utilizes an automatic bias control (ABC) circuit to maintain the bias voltage applied to the external modulator at a predetermined level required to provide the necessary separation between logic levels. The ABC circuit generates a dither signal and functions to digitally compare the phase of the dither signal to the phase of the optical signal produced by the external modulator. A phase comparator (e.g., D-type flip-flop) is used to monitor any drift in the optimum bias point of the modulator and generate an output correction signal by continuously adjusting the level of the DC bias voltage applied to the external modulator.

Modulator-based lightwave transmitter

Growing community of inventors

Wescosville, PA, United States of America

Yong-Kwan Park