Abstract: A method of communicating an optical signal includes generating an optical signal at a bit rate of at least 2.5 Gb/s. The optical signal including at least thirty optical channels. In one particular embodiment, at least some of the thirty optical channels reside within a 1567-1620 nanometer wavelength range. The method also includes receiving the optical signal at a ROPA that includes a rare-earth doped optical fiber. In addition, the method includes introducing a pump signal to a communication span of the unrepeatered optical communication system. The pump signal operable to amplify the optical signal by Raman amplification within the communication span and including at least one pump signal wavelength operable to excite the rare-earth doped fiber. The method further includes receiving the optical signal after the optical signal has traversed at least 200 kilometers of the communication span.

Abstract: A method of communicating an optical signal includes generating an optical signal at a bit rate of at least 2.5 Gb/s. The optical signal including at least thirty optical channels. In one particular embodiment, at least some of the thirty optical channels reside within a 1567-1620 nanometer wavelength range. The method also includes receiving the optical signal at a ROPA that includes a rare-earth doped optical fiber. In addition, the method includes introducing a pump signal to a communication span of the unrepeatered optical communication system. The pump signal operable to amplify the optical signal by Raman amplification within the communication span and including at least one pump signal wavelength operable to excite the rare-earth doped fiber. The method further includes receiving the optical signal after the optical signal has traversed at least 200 kilometers of the communication span.

Abstract: A method of communicating an optical signal includes generating an optical signal at a bit rate of at least 2.5 Gb/s. The optical signal including at least thirty optical channels. In one particular embodiment, at least some of the thirty optical channels reside within a 1567-1620 nanometer wavelength range. The method also includes receiving the optical signal at a ROPA that includes a rare-earth doped optical fiber. In addition, the method includes introducing a pump signal to a communication span of the unrepeatered optical communication system. The pump signal operable to amplify the optical signal by Raman amplification within the communication span and including at least one pump signal wavelength operable to excite the rare-earth doped fiber. The method further includes receiving the optical signal after the optical signal has traversed at least 200 kilometers of the communication span.

Abstract: Bidirectional transmission over a single optical fiber is obtained in an optical communications system by using a three port circulator in customer premises equipment together with an optical fiber amplifier and a narrow band filter. The fiber amplifier can be locally or remotely pumped. The acousto-optic modulator is advantageously used because it reduces the coherent Rayleigh noise by detuning upstream and downstream wavelengths.

Abstract: This invention describes a tunable optical filter to be used in an optical communication system. The filter of this invention has a pair of resonator cavities which are cascaded. The lengths of each of the cavities change simultaneously with the change in length of a piezoelectric sleeve which contacts a reflective surface of each of the cavities through spacers. The sleeves and spacers are set so as to move the reflecting surfaces of the cavities along a single axis in response to a single control signal. When optical signals are passed through the two cavities and when the ratio of the length of the cavities is adjusted to a predetermined ratio of integers, the resonator cavity will resonate at a desired wavelength.

Abstract: An optical message distribution system is described which includes both a plurality of message sources and destinations. Each optical message includes a destination address portion and a data portion containing data signals. At a message source, an encoder generates, for each data signal of one kind, an optical pulse whose time position relative to a frame is indicative of a message destination address. An optical summer, common to all message sources combines the optical pulses onto an optical transmission medium and transmits them to an optical decoder associated with the each message destination. Each optical decoder determines if the time position of a received optical pulse relative to the frame is equal to a preset time delay, and if so, generates a data pulse of the one kind for the message destination.

Abstract: An optical communication system is described wherein a message pathway is indicated by a destination address, manifested by an address time interval between a reference optical signal and an address optical signal. The optical communication system includes an optical switch for directing messages onto selected pathways. The switch includes a gate summer, and a reference circuit for applying a destination address portion of a message to the gate summer. A first delay circuit also applies the address portion of the message to the gating summer, while retarding it by a first address time interval. The gate summer sums the address portion from the reference circuit and the retarded address portion to produce a gating signal when the reference optical signal and address optical signal are time coincident. Switch means are further provided which are responsive to the gating signal to direct the message along a first selected pathway.

Abstract: A tunable optical filter having a number cascaded resonator cavities with each cavity having electro-optic material in its interior. The resonator cavities will resonate at a select wavelength when the index of refraction of the electro-optic material is changed to a predetermined value in response to only a single control voltage. The index of refraction of the electro-optic material is adjusted to a predetermined value by application of the single control voltage to one of a pair of electrodes which are on opposite sides of the resonator cavities.

Abstract: A communication system and method for transmitting information in the form of binary digital data to be transmitted is encoded into two separate two level sequences S1 and S2 such that the first occurrence of a logic "1" is encoded into the same level in both sequences and each subsequent occurrence of a logic "1" is encoded into the level opposite of the previous level representing a logic "1" in each of the sequences S1 and S2, and the first occurrence of a logic "0" is encoded into opposite levels in sequences S1 and S2 and every subsequent occurrence of a logic "0" is encoded into the level opposite of the previous level representing a logic "0" in each of the sequences S1 and S2. The two encoded streams drive optical signal producing means of respectively different wavelengths and the two optical signals are transmitted over a wavelength-multiplexed fiber-optic link.