Abstract: 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; resulting in much reduced complexity and cost for the final receiver.

Abstract: 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, wherein said optical delays are selected to be substantially less than a bit period of the optical channel.

Abstract: 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; resulting in much reduced complexity and cost for the final receiver.

Abstract: 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, wherein said optical delays are selected to be substantially less than a bit period of the optical channel.

Abstract: A tunable laser device (1) comprises integrally formed first and second ridge waveguides (5, 6). A longitudinally extending ridge (12) defines first and second light guiding regions (19, 20) of the first and second waveguides (5, 6) A plurality of first and second slots (27, 28) extending laterally in the ridge (12) adjacent the first and second waveguides (5, 6), produce first and second mirror loss spectra of the respective first and second waveguides (5, 6) with minimum peak values at respective first and second wavelength values. The spacing between the second slots (28) is different to that between the first slots (27) so that with one exception the minimum peak values of the first and second mirror loss spectrum occur at different wavelength values. The first and second waveguides (5, 6) are independently pumped with variable currents to selectively vary the common wavelength at which the minimum peak values of the first and second mirror loss spectra occur to produce Vernier tuning of the device.

Abstract: A laser device includes a ridge waveguide having an active layer between upper and lower cladding layers. A ridge formed in the upper cladding layer defines the width of a light guiding region in the active layer, and is formed so that a portion of the light guiding region extends into the ridge. A plurality of reflecting slots extend across and into the ridge to a depth sufficient to extend into the extending portion in order that the reflectivity of each slot is on the order of 2%. The slots intersect more than 20% of the total mode energy in the light guiding region, and this in combination with the gain of the active layer facilitates lasing within the light guiding region independently of the reflectivity of end facets of the waveguide. The laser device is particularly suitable for integrally forming with other optical components on a single semiconductor chip.

Abstract: 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%.

Abstract: A tunable laser device (1) comprises integrally formed first and second ridge waveguides (5, 6). A longitudinally extending ridge (12) defines first and second light guiding regions (19, 20) of the first and second waveguides (5, 6) which communicate with each other. A plurality of first slots (27) extending laterally in the ridge (12) adjacent the first waveguide (5), and a plurality of second slots (28) extending laterally in the ridge (12) adjacent the second waveguide (6) produce first and second mirror loss spectra of the respective first and second waveguides (5, 6) with minimum peak values at respective first and second wavelength values.