Abstract: A WDM transmitter comprising an array of M pump lasers multiplexed by an M×N multiplexer, in the form of a coupler, and used to feed an array of N optically pumped fiber lasers emitting at wavelengths &lgr;1, &lgr;2, . . . &lgr;N. The parameter M determines the number of pump lasers as well as the number of inputs of the pump-multiplexing coupler and can be smaller or equal to parameter N that determines the number of optically pumped lasers. The fiber laser outputs are passed through N isolators before entering N modulators were the signals are monolithically modulated. The outputs of the modulators are passed through an array of N tunable attenuators. Finally all the individual channel outputs are recombined into a single output in a combiner. The output will typically lead to an optical network. The proposed architecture may also be used for optical amplifiers, especially fiber-based optical amplifiers.

Abstract: Optical code division multiple access (OCDMA) coder:decoder gratings have been fabricated. The modulated refractive index profile that makes up the OCDMA coder:decoder grating incorporates changes in polarity between OCDMA chips by discrete phase shifts, thereby to provide bipolar coding through phase modulation. (In another embodiment quadrupolar coding is achieved). For NRZ modulation, each grating section is either in phase with, or has a predetermined phase shift relative to, the preceding grating section, depending on whether the OCDMA signature has a change in polarity between chips. RZ modulation is also possible. Results are presented from specific examples of bipolar OCDMA with NRZ modulation, which show higher data rates (10 Gbit/s), shorter chip-lengths (6.4ps) and far longer code sequences (63 bits) than previously demonstrated. Other embodiments relate to optical packet switching, for example using the Internet Protocol (IP) or Asynchronous Transfer Mode (ATM).

Abstract: An optical waveguide grating if formed in a waveguide of nominally uniform diameter. A grating characteristic is varied at positions along the grating in a substantially inverse relationship to the diameter of the waveguide at those positions.

Abstract: A hybrid optical transmission system comprising an optical transmitter and receiver. The transmitter includes an input for receiving an encoding signal and an encoder arranged to encode an optical signal with any one of a plurality of encoding signatures according to the encoding signal. The optical receiver comprises a grating decoder connected to receive the encoded optical signal from the input, the grating decoder incorporating a decoding signature complementary to a matched one of the encoding signatures so as to decode the encoded optical signal when encoded with the matched one of the encoding signatures. A hybrid system is thus provided that uses (passive) grating decoders at the receiver in combination with active drive-signal-based encoders at the transmitter. In this way, flexibility can be retained for the transmitter hardware, whereas the advantages of grating decoders can be exploited at the receivers.

Abstract: An optical fiber, a section of length (Lgr) which is modulated in refractive index so as to form a grating with a plurality of characteristics reflection wavelength channels, has a refractive index modulation comprising an amplitude modulation having an underlaying higher frequency component defining the shape of the reflection profile of each of the wavelength channels and, superposed thereon, a lower frequency component of period P imposing repeated envelopes over the higher frequency component and defining the separation of the wavelength channels. In one embodiment, the lower frequency component has the shape of a sinc-function with varying refractive index (&dgr;n) and with discrete &pgr;-phase shifts (&dgr;&phgr;) each envelope, to form a sinc-sampled grating. Chirped multi-channel optical fiber gratings may thus be provided for dispersion compensation in long-haul transmission links.