The invention provides a solution for the full integration of a coherent receiver on Indium Phosphide (InP) or other material that has a number of advantages over current coherent receiver design. PIN waveguides can be reverse biased and forward biased to modify the mode effective index so as to realize an integrated polarization beam splitting function and the 90 degree optical hybrid. The fabrication tolerance is therefore greatly increased

The invention provides a system and method for measuring optical signal-to-noise-ratio (OSNR) in an optical communication system. A channel filter is adapted to select one specific optical communication channel from a wavelength-division-multiplexing (WDM) optical communication system, wherein the channel comprises an optical signal carrying digital bit information and noise from associated optical power amplifiers in the system. At least one optical delay interferometer is adapted to measure at least two interferograms of the noisy signal. The invention provides a mechanism for calculating the in-band OSNR from extinctions of the interferograms measured at different optical delays by referring to each other. Because of the self-reference between the two measurements, the system can follow any changes happening to the signal such as additional filtering, self (cross)-phase modulation, the bias and drive signal change of the modulator used to generate the optical signal.

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A laser device (1) comprises a ridge waveguide (2) comprising an upper cladding layer (5) and a lower cladding layer (6), between which is located an active layer (7). A ridge (8) formed in the upper cladding layer (5) defines the lateral width of a light guiding region (9) in the active layer (7). The ridge (8) is formed so that a portion (13) of the light guiding region (9) extends above the active layer (7) into the ridge (8). A plurality of lateral reflecting slots (15) extend laterally across the ridge (8) and extend into the ridge (8) to a depth sufficient to extend into the portion (13) of the light guiding region (9) which extends into the ridge (8) in order that the reflectivity of each lateral slot (15) is in the order of 2 %.

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A process for the preparation of a micro- or nano-sized product comprises preparing a sol, introducing the sol onto a substrate matrix before the gelation point of the sol has been reached, and applying a vacuum. The products of the process have a. diameter of from 1 to 10 micrometers and a controlled length of up to several millimetres, They can be used in detectors of sub-micron objects, including biological pathogens, integrated optics, cavity quantum electrodynamics, nonlinear optics and optical communications, temperature detectors, bio- and chemosensors, microchannels for optically and spectral controlled cell growth, optical mode converters, optical polarization converters, components for microelectrophoresis, light emitters, optical amplifiers and optical elements of quantum cryptographic systems.

Related:

Apparatus for determining the pulse width of ultra-short light pulses of an input repetitive light pulse signal comprises a two-photon absorption. detector (2) in the form of a microcavity (3) having an active region (4) located between top and bottom distributed Bragg reflectors (5,6). An optical fibre cable 16 directs the input light pulse signal combined with a reference repetitive light pulse signal normal to an incident surface (8) of the detector (2). The input light pulse signal is split in a polarisation light splitter (19) to form the reference light pulse signal which is passed through a delay line (23) to a polarisation light combiner (20) to be combined with the input light pulse signal, and directed at the incident surface (8) by the optical fibre cable (16).

Related:

A heterostructure self-pulsating laser device (1) comprising an active layer (5) with first and second cladding layers (6, 7) on respective opposite sides of the active layer (5) is grown on an n-substrate (2) of indium phosphide, the second cladding layer (7) being grown on the substrate (2), the active layer (5) being grown on the second cladding layer (7), and the first cladding layer (6) being grown on the active layer (5). A current blocking layer (12) is formed in the first cladding layer (6) and divides the first cladding layer (6) to form a distal cladding layer (15) and a proximal cladding layer (16) adjacent the active layer (5). A channel (14) defined by the current blocking layer (12) confines the current in the first cladding layer (6) and determines the width of the active light generating area of the active layer (5). The first and second cladding layers (6, 7) and the current blocking layer (12) are of grown doped indium phosphide. The first cladding layer (6) is doped to be a p-type layer and the second cladding layer (7) and the current blocking layer (12) are doped to be of n-type. The level of dopant in the current blocking layer (12) is approximately ten times greater than the level of doping in the first cladding layer (6) in order to establish an effective refractive index step in the lateral direction of the active layer (5) in order to confine light generated in the active layer (5). A continuous wave operating laser device is also described.

An optical delay device (1) comprises a photonic molecule (3) comprising a pair of identical optically coupled microspheres (8a, 8b) of light conducting material, the centres of which are located on a common axis of symmetry (10), and the outer surfaces (11) of which touch at (12) on the common axis of symmetry (10). An input fibre optic cable (14) directs an optical signal at the microsphere (8a) along an input optical path (18) which is disposed at an angle ? greater than zero to the common axis of symmetry (10), while the delayed optical signal is detected by an output fibre optic cable (16) along an output optical path (19) from the microsphere (8b) which is disposed at an angle a greater than zero to the common axis of symmetry (10). The input fibre optic cable (14) and the output fibre optic cable (16) are moveable relative to the photonic molecule (3) for facilitating varying of the angle ? an the angle a for in turn varying the delay to which the optical signal is subjected in the photonic molecule (3). Additionally, the microsphere (8a) is moveable along the common axis of symmetry (10) relative to the microsphere (8b) for further facilitating varying of the delay to which the optical signal is subjected in the photonic molecule (3).