Abstract: A wavelength division multiplex (WDM) optical network comprises a ring configuration of optical fiber links connecting a plurality of nodes and add and drop filters at each node connected in series within the ring. One or more of the filters are arranged to add or drop at least two selected adjacent wavelength channels of the WDM optical signal while allowing the remainder of the channels within the WDM signal to pass substantially unattenuated. The wavelength channels of each node are selected such as to maximize the number of adjacent wavelength channels at each node.

Abstract: A wavelength division multiplex (WDM) optical telecommunications network comprises a plurality of nodes interconnected by optical fiber waveguides. Communication traffic is communicated between nodes by optical radiation modulated with the communication traffic, the radiation being partitioned into aplurality (N) of wavelength channels each channel having a discrete non-overlapping waveband. Each node drops at least one of the wavelength channels to thereby define a connection to the node and adds at least one wavelength channel to the network to define a connection to another node of the network. The network is characterized is that at least one node has ascribed to it a fixed subset of the N wavelength channels and drops each of the wavelength channels of the fixed subset from the network.

Abstract: An optical add-drop filter for use in a communication system which is capable of communicating both supervisory traffic and communication traffic. Communication traffic is modulated onto first radiation occupying a first range of radiation wavelengths, and supervisory traffic is modulated onto second radiation occupying a second range of radiation wavelengths. When the first and second radiation is received at one or more of the nodes, it is then filtered in the add-drop filters associated therewith to isolate add channels, drop channels, a supervisory channel drop and a supervisory add from primary relatively-low attenuation paths of the filters. The add channels, the drop channels, and the supervisory channel drop and add are then isolated at secondary paths associated with, but not included in the primary paths.

Abstract: A wavelength division multiplex (WDM) optical network comprises a ring configuration of optical fiber links (4a-4f) connecting a plurality of nodes (2a-2f) and add (8) and drop (10) filters at each node (2a-2f) connected in series within the ring. One or more of said (8, 10) filters are arranged to add or drop at least two selected adjacent wavelength channels (&lgr;N, &lgr;M) of the WDM optical signal whilst allowing the remainder of the channels within the WDM signal to pass substantially unattenuated. The wavelength channels of each node are selected such as to maximise the number of adjacent wavelength channels at each node.

Abstract: The present invention provides a wavelength selective optical filter device (240) for receiving input radiation and outputting corresponding filtered output radiation, characterized in that the filter device (240) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators (330, 340, 360; 360, 400, 430) for filtering the input radiation to generate the output radiation, the filter device (240) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being retuned from the first wavelength (&lgr;1) to the second wavelength (&lgr;2) so that the filter device (240) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors (360, 430) which are electrostatically actuated to affect tuning of the resonators (330, 340, 360; 360, 400, 430).

Abstract: The present invention provides a wavelength selective optical filter device (240) for receiving input radiation and outputting corresponding filtered output radiation, characterized in that the filter device (240) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators (330, 340, 360; 360, 400, 430) for filtering the input radiation to generate the output radiation, the filter device (240) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being retuned from the first wavelength (&lgr;1) to the second wavelength (&lgr;2) so that the filter device (240) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors (360, 430) which are electrostatically actuated to affect tuning of the resonators (330, 340, 360; 360, 400, 430).

Abstract: The present invention provides a wavelength selective optical filter device (240) for receiving input radiation and outputting corresponding filtered output radiation, characterised in that the filter device (240) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators (330, 340, 360; 360, 400, 430) for filtering the input radiation to generate the output radiation, the filter device (240) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being returned from the first wavelength (&lgr;1) to the second wavelength (&lgr;2) so that the filter device (240) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors (360, 430) which are electrostatically actuated to affect tuning of the resonators (330, 340, 360; 360, 400, 430).

Abstract: The present invention provides a wavelength selective optical filter device (240) for receiving input radiation and outputting corresponding filtered output radiation, characterized in that the filter device (240) includes a plurality of at least partially mutually coupled Fabry-Perot optical resonators (330, 340, 360; 360, 400, 430) for filtering the input radiation to generate the output radiation, the filter device (240) being tunable from a first radiation wavelength to a second radiation wavelength by mutually detuning the resonators in a period where the resonators are being retuned from the first wavelength (&lgr;1) to the second wavelength (&lgr;2) so that the filter device (240) is substantially in a non-responsive state during the period. The resonators incorporate freely suspended mirrors (360, 430) which are electrostatically actuated to affect tuning of the resonators (330, 340, 360; 360, 400, 430).

Abstract: This invention relates to an optical sensor for testing a biochemical sample. The sensor includes a resonant mirror device 1 and a prism 2 disposed adjacent the device 1 for coupling an input beam of light to the device 1. The input beam of light having a comb spectrum with a uniform spacing between adjacent lines or bands of the spectrum is produced by a comb spectrum source 10. The comb spectrum may be produced by a diode laser with multiple longitudinal modes. The input beam of light is polarized by a polarizer 4 to provide equal TE and TM components. The resonant mirror device is arranged in the paths of said input beam of light such that resonance is excited for at least one of said components, An analyser 11 is arranged to receive said components of the beam of light reflected from the device 1 for producing an output beam having a spectrum including a series of bright and/or dark lines or bands corresponding to the lines or bands of the comb spectrum of the input beam.

Abstract: This invention describes a technique for improving the sensitivity of a resonant mirror sensor which has particular applications in areas involving sensing at an interface such as immunosensing using immobilized antibodies. By the introduction of a Bragg grating structure in the sensor, there is produced enhanced dispersion and hence enhanced sensitivity in the region close to the band edge. This improves the detection limit of the sensor without changing the composition or involving the sensor size and allows more sensitive operation at reduced incident angles.

Abstract: An optical resonant assembly which comprises a plurality of partially light-transmitting mirrors, a layer of photochromic material disposed between the mirrors, a light source providing a light beam of variable intensity incident on the layer of photochromic material and detecting means for determining transmittance values of said incident beam at different intensity levels, said photochromic material having a low quantum yield for bleaching with light of a wavelength corresponding to said light beam and being selected from pyran compounds of the general formula (I) below: ##STR1## wherein X and Y together represent a spiro-adamantylidene group or a spiro-carbocyclic or heterocyclic group or X and Y independently represent hydrogen, alkyl (preferably lower alkyl having 1 to 5 carbon atoms) or phenyl and R.sub.3 and R.sub.4 each independently represent hydrogen, alkyl, aralkyl, aryl, halogen or a heterocyclic group and R.sup.

Abstract: An optical resonant assembly which has at least two stable light transmittance values dependent on incident light beams. The assembly consists of a pair of parallel partially transmission mirrors with a photochromic layer placed therebetween which has a refractive index dependent upon the intensity of incident light beams. The parallel mirrors constitute a Fabry-Perot type resonator. The incident light beams have the effect of "couloring" or "bleaching" the photochromatic material.