Abstract: A multiwavelength transmitter comprises several laser sources (1) each configured to generate light of a different wavelength and a first array waveguide grating (2) arranged to direct light from each of the laser sources (1) into a first waveguide. The transmitter further comprises several electroabsorption modulators (7) each arranged to modulate light at one of the wavelengths with a respective data signal and a second array waveguide grating (6) arranged to direct each of said different wavelengths of light from the first waveguide to a respective one of the modulators (7). The optical modulators (7) are reflective optical modulators and the second array waveguide grating (6) is arranged to direct the modulated light reflected from each of the optical modulators (7) back into the first waveguide. An optical circulator (5) is provided in the first waveguide to couple modulated light from the second array waveguide grating (6) into an output waveguide.

Abstract: A multiwavelength transmitter comprises several laser sources (1) each configured to generate light of a different wavelength and a first array waveguide grating (2) arranged to direct light from each of the laser sources (1) into a first waveguide. The transmitter further comprises several electroabsorption modulators (7) each arranged to modulate light at one of the wavelengths with a respective data signal and a second array waveguide grating (6) arranged to direct each of said different wavelengths of light from the first waveguide to a respective one of the modulators (7). The optical modulators (7) are reflective optical modulators and the second array waveguide grating (6) is arranged to direct the modulated light reflected from each of the optical modulators (7) back into the first waveguide. An optical circulator (5) is provided in the first waveguide to couple modulated light from the second array waveguide grating (6) into an output waveguide.

Abstract: The present invention relates to a method of optical communication, in particular optical communication involving spectral filtering in a passive optical network. The method includes the steps of: (i) performing a first spectral filtering function on a source signal having a spectral width so as to generate a plurality of feeder signals that are spectrally spaced apart from one another; (ii) performing a respective noise reduction function on the feeder signals; (iii) combining the feeder signals over a common waveguide of the optical link; (iv) receiving the feeder signals carried over the optical link and modulating the received feeder signals so as to impose data thereon; and, (v) returning the modulated feeder signals over the optical link so as to communicate the imposed data. Because noise is reduced centrally, a simpler passive optical network can be achieved.

Abstract: A device and method for correcting for timing jitter of an optical data pulse in an optical transmission system. During transmission, a data pulse may suffer jitter. Its arrival time at a node may be temporally offset from its predicted arrival time. Data pulses are timed so that they may be received at a detector disposed downstream of the node at a predetermined time. The device includes a source of chirped optical pulses and a node, which has a first input arranged to receive a chirped optical pulse. The node has a second input arranged to receive a data pulse. The node includes an optical gate arranged to generate an output pulse in response to the first pulse and the data pulse received at the first and second inputs, respectively, having a wavelength dependent upon the time at which the data pulse is received at the second input. The device further includes an optically dispersive medium after passage through which, the output pulses are correctly retimed in order to correct for the timing jitter.

Abstract: There is provided an apparatus for processing a segment of x optical bit slots from a packet comprising y optical bit slots, each bit slot defining a respective one of first and second complementary logical states, within a time span shorter than or equal to the time for receipt of the packet. The apparatus including a segment replicator which generates serial copies of the segment of the packet, each copy residing within a respective word containing z bit slots, where z is equal to or greater than x; and a bit differential processor for processing successive bits of the successive copies of the segment in n successive processing steps, the product of n and z being less than or equal to y. The result of each processing step is output in sequence by the bit differential processor, the result of processing the segment being given by x successive bit slots of the output.

Abstract: A method of producing a planar waveguiding device having a core [10] and a cladding [17]. The cladding has groves [11,12] directly interfacing [15,16] with the core [10]. A layer of core glass [10] is deposited on the surface of a substrate [23,24]. This layer is etched to produce a shaped layer which includes a first core portion [10] having the same configuration as the intended core [10] and an expanded core portion [30] wherein the core glass extends beyond the intended core boundary. A glass covering layer [21] is deposited over the etched core glass and grooves [11,12] are produced by etching through the covering layer [21] and into said expanded core portion [30].

Abstract: A device and method for quantifying the amount of jitter experienced by an optical data pulse. During transmission data pulses may suffer jitter. Their arrival time at a node may be temporally offset from its predicted arrival time. Data pulses are timed so that they may be received at a detector disposed downstream of said node at a predetermined time. The device includes an optical AND gate, which has a first input arranged to receive a chirped pulse having a duration T, and whose wavelength varies in a monotonically over the duration of the pulse, the node having a second input arranged to receive a second data pulse. The node includes an optical gate arranged to generate an output pulse in response to the chirped pulse and the data pulse received at the first and second inputs, respectively, having a wavelength dependent upon the time at which the data pulse is received at the second input.

Abstract: A planar waveguiding device includes at least on section of core which is located between and adjacent to two grooves. The refractive index within the grooves is substantially equal to one and the grooves are located so that the evanescent fields of optical signals travelling in the core extend into the grooves. Preferably the grooves have a direct interface with the core and they extend through a layer located above the core into a layer located below the core. Where the cores have bends, e.g. bends with radii of curvature below 2 mm the grooves are located both inside and outside the bends.

Abstract: There is provided an apparatus for processing a segment of x optical bit slots from a packet comprising y optical bit slots, each bit slot defining a respective one of first and second complementary logical states, within a time span shorter than or equal to the time for receipt of the packet. The apparatus including a segment replicator which generates serial copies of the segment of the packet, each copy residing within a respective word containing z bit slots, where z is equal to or greater than x; and a bit differential processor for processing successive bits of the successive copies of the segment in n successive processing steps, the product of n and z being less than or equal to y. The result of each processing step is output in sequence by the bit differential processor, the result of processing the segment being given by x successive bit slots of the output.

Abstract: A clock signal at a divided clock rate is obtained from an optical signal stream at a higher clock rate. The optical signal stream at the higher clock rate is applied to an all-optical non- linear gate. There is feedback from the first output of the gate to its control input. The optical signal at a divided clock rate is present at a second output of the gate. The gate may comprise a non-linear loop mirror. A number of such gates may be cascaded in series to provide an output at a clock rate divided by 2n, where n is an integer.

Abstract: A device and method for quantifying the amount of jitter experienced by an optical data pulse. During transmission data pulses may suffer jitter. Their arrival time at a node may be temporally offset from its predicted arrival time. Data pulses are timed so that they may be received at a detector disposed downstream of said node at a predetermined time.

Abstract: An optical filter and method of filtering uses a multi-mode waveguide having a first number n modes and a second waveguide having a different number m modes are coupled in series, where n and m are integers and n>m, and where the interaction of different modes at the interface of the two waveguides filters an optical signal propagating through the waveguides to provide a desired response characteristic. A lateral offset between the central axes of the waveguides at their interface is changed to control the response of the filter. For a multiple wavelength optical source uses, a filter coupled in the optical cavity including a laser gain medium provides interaction of different modes at the interface of waveguides in the filter to filter an optical signal propagating in the cavity thereby providing an output signal with multiple peaks at different wavelengths with a predetermined spacing.