Lucent Technologies Inc.

Song Jiang

Yong-Kwan Park

Kyeong-Soo Kim

Reed K Even

Woojune Kim

Peter Van Eijk

Fengkun Liu

Piet Van Heyningen

Clinton R Giles

Piet Van Hevingen

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 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

A system and method for maintaining alignment between a source and router in a Wavelength Division Multiplexed (WDM) fiber optic network. In a preferred embodiment, a narrow band of the wavelengths emitted by the WDM source is designated as a monitor channel. The monitor channel is matched in wavelength to a fiber grating that is located in the optical path between the source and router so that the grating reflects the monitor channel light while allowing all other source light to pass through unimpeded. By monitoring the reflected light and adjusting the source wavelengths to maximize the amount of reflected light, alignment between the source and router is maintained.

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Whippany, NJ, United States of America

Song Jiang