Abstract: An optical signal transmission line includes a first fiber adapted to guide an optical signal therethrough and having a first ?, a second fiber adapted to guide the optical signal therethrough and having a second ? of less than or equal to about 100 nm at a wavelength of 1550 nm, and a ? compensating fiber adapted to guide the optical signal therethrough and having a third ? of greater than or equal to about 60 nm at a wavelength of 1550 nm. The first fiber, the second fiber and the ? compensating fiber are in optical communication, thereby defining an optical transmission line having a total dispersion and a total dispersion slope. The first ?, the second ? and the third ? cooperate such that the total dispersion is within the range of about 1.0 ps/nm-km?total dispersion?about ?1.0 ps/nm-km at a wavelength of 1550 nm, and the total dispersion slope is within the range of about 0.02 ps/nm2-km?total dispersion slope?about ?0.02 ps/nm2-km at a wavelength of 1550 nm.

Abstract: An optical amplitude modulator (16) has a first input (13) for receiving a continuous optical signal, a second input (17) for receiving a bipolar data encoded electrical signal, and a Mach-Zehnder interferometer transfer operation biased at V&pgr; for modulating the continuous signal based on the bipolar data encoded electrical signal for generating an AMI modulated optical signal having three electric field levels, +/−E and 0, and two power levels, 0 and P, such that the resultant modulated signal is both amplitude and phase modulated.

Abstract: An optical signal transmission line includes a first fiber adapted to guide an optical signal therethrough and having a first &kgr;, a second fiber adapted to guide the optical signal therethrough and having a second &kgr; of less than or equal to about 100 nm at a wavelength of 1550 nm, and a &kgr; compensating fiber adapted to guide the optical signal therethrough and having a third &kgr; of greater than or equal to about 60 nm at a wavelength of 1550 nm. The first fiber, the second fiber and the &kgr; compensating fiber are in optical communication, thereby defining an optical transmission line having a total dispersion and a total dispersion slope. The first &kgr;, the second &kgr; and the third &kgr; cooperate such that the total dispersion is within the range of about 1.0 ps/nm-km≧total dispersion≧about −1.0 ps/nm-km at a wavelength of 1550 nm, and the total dispersion slope is within the range of about 0.02 ps/nm2-km≧total dispersion slope≧about −0.

Abstract: An optical signal amplifier includes a Raman fiber amplifier and a semiconductor optical amplifier. The Raman fiber amplifier utilizes pump radiation to amplify the optical signal resulting in an amplified optical signal. The semiconductor optical amplifier receives the amplified signal amplifying the amplified signal resulting in a twice amplified signal.

Abstract: Disclosed is a negative total dispersion waveguide fiber having low attenuation and sufficiently good resistance to bend loss that attenuation is not impacted by cabling or otherwise buffering the waveguide. The total dispersion slope of the waveguide fiber is positive so that the zero dispersion wavelength is greater than 1600 nm. The waveguide fiber may advantageously be used in a link having a distributed feedback laser as a signal source. The negative dispersion of the waveguide in accordance with the invention compresses the launched signal pulse when the laser is positively chirped. The laser is operated at optimum bias, which results in positive chirp, but no dispersion penalty is incurred in the link. The waveguide fiber in accordance with the invention may also be advantageously used as a dispersion compensating fiber in a high performance multiplexed telecommunications link.

Abstract: A flexible bit rate clock recovery unit is provided for recovering a clock signal from an input data signal, where the input data signal is transmissible at different bit rates. The flexible bit rate clock recovery unit includes a plurality of fixed rate clock recovery units, where each fixed rate clock recovery units is operative at a different bit rate to extract an intermediary clock signal from the input data signal; a comparator for generating an encoded data signal based on an amplitude characteristic of each of the intermediary clock signals, where the encoded data signal is indicative of the clock signal associated with the input data signal; and a selector for selecting one of the intermediary clock signals based on the encoded data signal, thereby recovering the clock signal from the input data signal.

Abstract: A fiber laser system including multiple fiber lasers fabricated to emit at respective different wavelengths when optically pumped by radiation at a pump wavelength. A pump laser emits the pump radiation and pumps one or more of the fiber lasers. The outputs of the fiber lasers are recombined onto a transmission fiber, preferably for use in a wavelength-division multiplexing (WDM) telecommunication system. In one set of embodiments, an optical switch switches the pump radiation to only one of the fiber lasers. A second switch controlled in correspondence to the first switch or a passive combiner, preferably a wavelength-division multiplexer, directs the output of the lasing fiber to an optical output path. In another embodiment, the one pump laser simultaneously pumps all the fiber lasers. One or more pump laser may be placed in parallel, and their outputs are combined. The parallel pump lasers may either be individually activated for redundancy or simultaneously operated for higher power.

Abstract: Bandwidth reduction methods and apparatus that offset the effects of dispersion on a signal transmitted through an optical fiber. The apparatus and methods employ a generator of modulated optical signals in cascade with a modulator. One of the generator and the modulator may be an optical intensity or amplitude modulator and the other a phase (or frequency) modulator. With the application of specific signals, the cascaded generator and modulator produce an optical signal with reduced energy in one half of the transmission bandwidth. One important benefit in the method is the fact that by exploiting the less obvious spectral characteristics of single sideband signals, a simple modulator design is achieved. All of the designs exploit a method of generating analytic signals via hybrid modulation.

Abstract: A signal processing circuit, the signal processing circuit comprising first and second waveguides, a series of successive couplers C.sub.i between the first and second waveguides, the couplers being spaced from each other along the first and second waveguides, the first and second waveguides having a delay differential .DELTA.L.sub.k between successive couplers C.sub.k-1 and C.sub.k, the delay differentials .DELTA.L.sub.k not being all the same. The first and second waveguides preferably have delay differentials between successive directional couplers defined by.beta..DELTA.L.sub.k =.beta.n.sub.k .DELTA.L+.PHI..sub.kwhere n.sub.k is a set of co-prime positive integers, .beta. is defined by .beta.+2.pi.n.sub.eff /.lambda., .DELTA.L is defined by .DELTA.L=c/n.sub.eff .DELTA.f, c is the speed of light in a vacuum, n.sub.eff is the effective refractive index of the conduit, .lambda. is a wavelength selected from a range of carrier wavelengths .lambda..sub.1 . . . .lambda..sub.

Abstract: Apparatus for generation of broadband vestigial sideband (VSB) signals primarily for transmission over optical fibers in which the carrier frequency is in the infrared portion of the electromagnetic spectrum. The modulating signal is normally a broadband digital signal. The apparatus includes an optical fiber, an optical signal source coupled to a modulator with first and second modulation signals modulating the carrier optical signal, plus a method of adding carrier optical signal to the modulator output optical signal and coupling to an output optical fiber. The modulation signals are selected such that an output optical signal transmitted along the optical fiber from the modulator has a vestigial single sideband. Part of the carrier optical signal is transmitted with the output optical signal through the use of a bypass loop or through an appropriate combination of the first and second modulation signals.