Abstract: A wavelength monitor and control system and method for a WDM optical transmission system is disclosed. The system comprises a heterodyne-based detection device with a real-time externally calibrated tunable laser.

Abstract: A gas blocking device is used in an optical fiber repeater or other device to prevent the passage of gas, for example, to prevent nitrogen from escaping from a pressurized housing through a fiber holding tube or pigtail. The gas blocking device includes a fiber containing body, a fiber organizing insert, and a locking member securing the insert to one end of the body. The fiber containing body is attached to one end of the fiber holding tube. The fibers extend from the fiber holding tube through a passageway in the body, and each of the fibers extends through a fiber receiving hole in the fiber organizing insert. The insert engages the body such that the insert is prevented from rotating with respect to the body and the fibers are protected against microbending and other damage. A material, such as hot melt glue, fills at least a portion of the body and surrounds the fibers to block the gas from entering the fiber holding tube.

Abstract: An isothermal fiber optic tray is used to hold optical fiber, such as erbium doped fiber in an erbium doped fiber amplifier (EDFA). The isothermal fiber optic tray comprises a thermally conductive inner structure providing a substantially isothermal cavity. An insulating outer structure is positioned adjacent first and second sides of the thermally conductive inner structure.

Abstract: A method of repairing a slope-matched cable system that leaves the net chromatic dispersion of the system nominally unchanged comprises removing a portion of the slope-matched cable system that is faulted, either the cable or a repeater, and constructing a replacement cable portion from two N-P cable lengths having negative dispersion fibers and positive dispersion fibers and a P cable length having positive dispersion fibers. The N-P cable lengths are coupled on each side of the P cable length and the replacement cable portion is connected to the slope-matched cable where the faulted cable was removed. The method also accounts for the extra cable that necessarily has to be added during the repair and for the replacement of a faulted repeater.

Abstract: A cable termination arrangement is used to terminate cables, such as armored fiber optic cables, to a connecting structure, such as a cable joint or coupling. Strength members, such as aramid rods, extending along the cable are terminated with radial termination members, such as crimping ferrules. The radial termination members extend into a termination cavity within the connecting structure and are spaced substantially equally, for example, using separators. An epoxy or other suitable retaining material encases the radial termination members, strength members, and separators.

Abstract: A system and method for optimizing dispersion in an optical transmission line is provided. The system and method comprise measuring the amplitude of a d.c. voltage component of a synchronously demodulated data signal of at least one wavelength channel by an in-phase carrier at the baud frequency of the wavelength channel. In an alternative embodiment, the system and method comprise measuring the IF amplitude of the resulting a.c. signal of a data signal of the at least one wavelength channel comprising a received RZ signal mixed with a local oscillator, whose frequency differs from the wavelength channel baud by a relatively small amount, somewhere on the order of about 100 kHz.

Abstract: An apparatus for retaining and protecting spliced optical fibers. Optical fibers forming an extensive network, extending a great distance, are spliced together to provide the communication medium for the network. The apparatus includes a joint box for protecting the splices. Within the joint box is at least one arcuate-shaped splice retainer. The retainer secures the splices in a static position to prevent them from being damaged. Also, the retainer may include more than one arcuate layers for storing the splices. The arcuate layers organize the splices, so they are readily identifiable and accessible. In addition, the arcuate layers make efficient use of the limited space available for storing the splices. The joint box includes a center shelf longitudinally dividing the joint box into two compartments. To accommodate more splices, an arcuate retainer may be provided in each compartment by mounting an arcuate retainer on each side of the shelf.

Abstract: An apparatus for measuring the noise figure in optical amplifiers employed for large bandwidth applications such as dense wavelength division multiplexing systems. A booster amplifier coupled to a light source increases the average power associated with a plurality of optical channels. A periodic filter is coupled to the booster amplifier to reflect noise between each of the optical channels across the predetermined bandwidth. An amplifier under test is coupled to the periodic filter and the noise figure associated with the amplifier under test is measured.

Abstract: A method and apparatus is provided that yields improved performance of both single channel and WDM long-distance optical transmission systems by synchronously modulating of the transmitted signal's amplitude. An amplitude modulator receives an optical signal onto which data has been modulated at a predetermined frequency. The modulator re-modulates the amplitude of the optical signal in a continues fashion with a waveform that is periodic, whose fundamental frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. The resulting signal (which is neither a pure NRZ or RZ signal) is more tolerant to the distortions usually found in lightwave transmission systems, thus giving superior transmission performance.

Abstract: A test apparatus includes a broadband noise source, a test station, and a spectrum analyzer. A method using the test apparatus to measure the spectral gain of an erbium doped fiber amplifier (EDFA) under test includes steps of providing an optical signal from a broadband noise source to an input of the EDFA under test, measuring a power at a test wavelength at an output of the EDFA under test, adjusting the test wavelength, and repeating the steps of measuring and adjusting for a predetermined number of times.

Abstract: An optical fiber holding structure is used to restrain high fiber count fibers or to provide splice protection in a cable joint. Layers of fibers are inserted between a compliant splint member and a semi-rigid splint member, which are positioned within an outer gripping tube such as a heat shrink tube. Optionally, an internal support can be positioned between the layers of fibers. The assembly is heated causing the heat shrink tube to apply a gripping force to the splint members and fibers supported therebetween. Where more than two layers of fibers are being restrained, internal supports can be positioned between each of the fiber layers. One type of internal support includes a rigid beam coated with a compliant material.

Abstract: A system and method for controlling optical amplifier pumps. A path average intensity detector is provided for detecting a path average intensity for transmitted optical signals. In response to the detected path average intensity or a variation in path average intensity, a pump parameter controller dynamically adjusts at least one pump parameter of at least one amplifier to achieve a desired path average intensity.

Abstract: A method and system by which a wide bandwidth continuous wave (CW) or substantially continuous wave composite (SCWC) pump with a flat spectrum is utilized to amplify an information-carrying signal. By using a wide bandwidth CW pump, substantially no ripple is introduced to the signal being amplified by the Raman amplifier.

Abstract: A lightwave communication system is provided that includes first and second optical transmitters/receivers remotely located with respect to one another. First and second optical transmission paths couple the first transmitter/receiver to the second transmitter/receiver for bidirectionally transmitting optical information therebetween. First and second doped optical fibers are respectively disposed in the first and second optical transmission paths. Optical pump energy is supplied by first and second optical pump sources. The first optical pump source generates Raman gain in the first transmission path and the second optical pump source generates Raman gain in the second transmission path. A first optical coupler is provided for optically coupling pump energy from the first pump source to the second-doped optical fiber and a second optical coupler is provided for optically coupling pump energy from the second pump source to the first doped optical fiber.

Abstract: An optical communication system is provided that includes first and second optical transmitters/receivers remotely located with respect to one another and which are coupled together by first and second optical transmission paths for bidirectionally transmitting optical information therebetween. First and second optical amplifiers are respectively disposed in the first and second optical transmission paths. At least one loop-back path optically couples a portion of a WDM optical signal from the first to the second transmission path. The loop-back path includes a filter for transmitting a monitoring channel but not a data channel included in the optical signal portion traversing the loop-back path.

Abstract: A wavelength division multiplex optical system includes a WDM combiner to provide a source signal, at least one transmitter coupled to an input of the WDM combiner, a broadband noise source, and a filter coupled between the broadband noise source and another input of the WDM combiner. In one embodiment, the filter is an optical notch filter. In an alternative embodiment, the filter includes a WDM demultiplexer coupled through plural filters to provide a plurality of noise signals and a WDM multiplexer coupled through at least one filter of the plural filters to respective noise signals.

Abstract: A method of increasing capacity on a long-haul undersea cable system having at least one optical fiber, said method comprising interleaving counter-propagating forward-propagating and backward-propagating signals in forward and backward channels on a common optical fiber, wherein the wavelength offset between said forward and backward channels is typically half of the channel spacing of co-propagating signals.

Abstract: A system and method for controlling gain shape in a Raman amplifier including a plurality of pumps. The pumps produce a spectral distribution of output power characteristic. A feedback control system provides one or more feedback control signals in response to the amplifier output for adjusting pump parameters to achieve a desired spectral distribution of output power characteristic.

Abstract: Packets are received at a first boundary node of a long haul optical communication network which may either interconnect originating and destination communication networks or form an integral part of a single end-to-end network. Packets are reclassified to reflect a higher priority of transmission than non-long haul bound packets, as by marking them with an indication of a modified priority level of transmission. Reclassified packets are transmitted over a long-haul optical link to a second boundary node. So that the modified priority level employed in the long-haul network may be understood by a destination network, packets arriving at the second boundary node may be re-mapped or reclassified to a value recognized as being of at least equal and, preferably, higher priority than that originally established by the originating network and/or first bounary node.

Abstract: A system and method for controlling optical amplifier pumps. A path average intensity detector is provided for detecting a path average intensity for transmitted optical signals. In response to the detected path average intensity or a variation in path average intensity, a pump parameter controller dynamically adjusts at least one pump parameter of at least one amplifier to achieve a desired path average intensity.