Abstract: A method and apparatus is provided for managing chromatic dispersion in an NRZ-based WDM long-haul optical transmission system so that nonlinearities are reduced, especially those at the edge channels of the band. The method includes using between 500 ps/nm and 2000 ps/nm of residual dispersion and a 40%/60% pre/post DCU split ratio when the channel wavelengths are shorter than the zero dispersion wavelength. Using these dispersion compensation rules, the nonlinear propagation effects in NRZ-based WDM systems is reduced, thus allowing for higher optical power per channel and/or longer transmission distances.

Abstract: A system, amplifier and method are provided for amplifying an optical signal in an optical communications system where spans between amplifiers may vary. The system includes a Raman amplifier variable gain portion and an EDFA gain portion. The amount of Raman amplifier gain is chosen to trade off accumulation of noise with accumulation of multi-path interference. This variable Raman gain is used to equalize the loss of each span so that the amount of optical power supplied at the input of the EDFA gain portion is substantially constant throughout the system.

Abstract: Dispersion may be managed in a branched optical network by using transmission segments having a single period segment dispersion map. One or more of such segments may be coupled to network nodes such as terminals or branching units such that dispersion may be managed even when the network is reconfigured. In one embodiment, a single period segment dispersion map provides dispersion compensation at the ends of the segment. In another embodiment, a single period segment dispersion-map provides dispersion compensation at the middle of the segment.

Abstract: A method of compensating for chromatic dispersion in an optical signal transmitted on a long-haul terrestrial optical communication system including a plurality of spans, including: allowing chromatic dispersion to accumulate over at least one of the spans to a first predetermined level; and compensating for the first pre-determined level of dispersion using a dispersion compensating fiber causing accumulation of dispersion to a second predetermined level. There is also provided a hybrid Raman/EDFA amplifier including a Raman portion and an EDFA portion with a dispersion compensating fiber disposed therebetween. An optical communication system and a method of communicating an optical signal using such a Raman/EDFA amplifier are also provided.

Abstract: A method of compensating for chromatic dispersion in an optical signal transmitted on a long-haul terrestrial optical communication system including a plurality of spans, including: allowing chromatic dispersion to accumulate over at least one of the spans to a first predetermined level; and compensating for the first pre-determined level of dispersion using a dispersion compensating fiber causing accumulation of dispersion to a second predetermined level. There is also provided a hybrid Raman/EDFA amplifier including a Raman portion and an EDFA portion with a dispersion compensating fiber disposed therebetween. An optical communication system and a method of communicating an optical signal using such a Raman/EDFA amplifier are also provided.

Abstract: A communication system including a repeatered trunk path and one or more unrepeatered branch segments coupled to the trunk path through associated submarine branching units. Each of the branch segments may be configured to carry at least the same channel capacity as the trunk path and may have a length greater than the average repeater spacing in the trunk path.

Abstract: Dispersion may be managed in an optical network configured to transmit differential phase shift keying (DPSK) modulated signals by allowing accumulation of dispersion to thousands of ps/nm before compensating. A dispersion map providing a negative average dispersion and a minimum dispersion wavelength outside of the signal band may be employed.

Abstract: A system, amplifier and method are provided for amplifying an optical signal in an optical communications system where spans between amplifiers may vary. The system includes a Raman amplifier variable gain portion and an EDFA gain portion. The amount of Raman amplifier gain is chosen to trade off accumulation of noise with accumulation of multi-path interference. This variable Raman gain is used to equalize the loss of each span so that the amount of optical power supplied at the input of the EDFA gain portion is substantially constant throughout the system.

Abstract: An apparatus and method directed to testing and optimizing performance of an optical transmission system is disclosed, including at least one broadband dispersion compensation unit (DCU) or at least one depolarization device. The depolarization device may be used alone or in combination with the at least one broadband DCU. A method for optimizing performance of data channels in initial loading (IL) and full loading (FL) configurations of the optical transmission system is also disclosed.

Abstract: A method and apparatus is provided for managing chromatic dispersion in an NRZ-based WDM long-haul optical transmission system so that nonlinearities are reduced, especially those at the edge channels of the band. The method includes using between 500 ps/nm and 2000 ps/nm of residual dispersion and a 40%/60% pre/post DCU split ratio when the channel wavelengths are shorter than the zero dispersion wavelength. Using these dispersion compensation rules, the nonlinear propagation effects in NRZ-based WDM systems is reduced, thus allowing for higher optical power per channel and/or longer transmission distances.

Abstract: A WDM optical communication system is provided that includes a transmitter and a receiver. An optical fiber transmission path couples the transmitter to the receiver. The transmission path includes at least one repeater having an optical amplifier located therein. A dispersion compensator is disposed at an intermediate point along the transmission path. The intermediate point is located outside of the repeater. The compensator includes a wavelength routing device for dividing a signal having a prescribed bandwidth into a plurality of distinct sub-bands. A plurality of output paths is provided for respectively receiving the plurality of distinct sub-bands. The dispersion compensator also includes a dispersion compensating optical element coupled to each of the output paths. Each dispersion compensating optical element substantially compensates for dispersion at a prescribed wavelength within the bandpass of its respective sub-band.

Abstract: Collisions between solitons in different frequency channels are one of the major sources of errors in transmission systems that utilize wavelength division multiplexing (WDM). Moreover, because standard transmission lines have lumped amplification, the four-wave mixing fields from soliton collisions grow uncontrollably, adding amplitude and timing jitter to the jitter due to ideal soliton collisions. These problems are addressed by using a specific dispersion map to implement dispersion management, by which it is possible to significantly reduce the collision-induced timing jitter and to improve system performance even in comparison with that provided by an ideal, exponentially decreasing dispersion fiber.

Abstract: A method and apparatus is provided for monitoring an optical transmission path through an optical transmission system supporting bidirectional communication between first and second terminals along first and second optical transmission paths. The first transmission path includes at least one optical amplifier located therein. In accordance with the method, a test signal is generated, which is formed by a superposition of first and second optical tones located at first and second wavelengths, respectively. The first and second wavelengths are within the bandwidth of the optical amplifier. The amplitude and phase of the first and second optical tones are arranged so that the test signal has a substantially constant intensity over a modulation cycle of the first and second optical tones. The test signal is transmitted from the first terminal along the first optical transmission path and through the optical amplifier.

Abstract: A method and apparatus is provided for compensating for dispersion in a wavelength division multiplexed (WDM) optical communication system. The system includes a transmitting and receiving terminal for transmitting and receiving, respectively, an optical signal having a plurality of channels, and an optical fiber transmission path coupling the first and second terminals. The fiber transmission path has a dispersion substantially equal to zero for a selected channel, positive dispersion for a first set of channels, and negative dispersion for a second set of channels. The method begins by providing positive dispersion compensation to the second set of channels at one of the terminals. Negative dispersion compensation is provided to the first set of channels, also at one of the terminals.

Abstract: A WDM optical communication system is provided that includes a transmitter and a receiver. An optical fiber transmission path couples the transmitter to the receiver. The transmission path includes at least one repeater having an optical amplifier located therein. A dispersion compensator is disposed at an intermediate point along the transmission path. The intermediate point is located outside of the repeater. The compensator includes a wavelength routing device for dividing a signal having a prescribed bandwidth into a plurality of distinct sub-bands. A plurality of output paths is provided for respectively receiving the plurality of distinct sub-bands. The dispersion compensator also includes a dispersion compensating optical element coupled to each of the output paths. Each dispersion compensating optical element substantially compensates for dispersion at a prescribed wavelength within the bandpass of its respective sub-band.

Abstract: A method is provided for determining the system performance of an optical transmission system that supports an optical signal having a plurality of channels. The method begins by selecting a set of parameters defining characteristics of the transmission system. Exemplary parameters include, for example, the system's length, bit rate, the number of amplifiers and channels employed, and the wavelengths of the channels and their respective power levels. The method continues by determining a baseline value of the system performance that accounts for fiber loss, optical amplifier gain and noise, and system gain equalization. Next, a first penalty to the baseline system performance is determined. The first penalty arises from a nonlinear interaction between the optical signal and amplified spontaneous emission. A second penalty to the baseline system performance is then determined. The second penalty arises from self-phase modulation and cross-phase modulation.

Abstract: A WDM optical communication system is provided that includes a transmitter and a receiver. An optical fiber transmission path couples the transmitter to the receiver. The transmission path includes at least one repeater having an optical amplifier located therein. A dispersion compensator is disposed at an intermediate point along the transmission path. The intermediate point is located outside of the repeater. The compensator includes a wavelength routing device for dividing a signal having a prescribed bandwidth into a plurality of distinct sub-bands. A plurality of output paths is provided for respectively receiving the plurality of distinct sub-bands. The dispersion compensator also includes a dispersion compensating optical element coupled to each of the output paths. Each dispersion compensating optical element substantially compensates for dispersion at a prescribed wavelength within the bandpass of its respective sub-band.

Abstract: Collisions between solitons in different frequency channels are one of the major sources of errors in transmission systems that utilize wavelength division multiplexing (WDM). Moreover, because standard transmission lines have lumped amplification, the four-wave mixing fields from soliton collisions grow uncontrollably, adding amplitude and timing jitter to the jitter due to ideal soliton collisions. These problems are addressed by using a specific dispersion map to implement dispersion management, by which it is possible to significantly reduce the collision-induced timing jitter and to improve system performance even in comparison with that provided by an ideal, exponentially decreasing dispersion fiber.