Abstract: An optical transmission network comprises a multi-wavelength source (7) shared between multiple sets of client side equipment for manipulating electrical signals. A first wavelength selective routing element (5) is connected to the multi-wavelength source (7). Each set of client-side equipment (1) comprises an optical modulator (3) connected to the first wavelength selective routing element (5) and an optical receiver (2). A second wavelength selective routing element (6) is connected to the optical receiver (2) and is operative to direct incoming signals from one or more remote locations to the optical receiver (2). The network provides a WDM architecture solution for networks whereby the cost of implementing and running client side equipment (1) is reduced by not having the WDM source (7) within the client side equipment (1).

Abstract: An optical amplifier has a low polarization dependent gain. The amplifier includes a gain medium including a plurality of adjoining semiconductor layers to provide optical gain wherein the adjoining semiconductor layers define one or more quantum wells for electrons and are operative to provide both direct and indirect electron-hole transitions in the gain medium. A first quantized electron energy level in the conduction band and a first quantized hole energy level in the valence band is located in a first layer. A further first quantized hole energy level in the valence band is located in an adjacent second layer.

Abstract: The present invention provides a current blocking structure for electronic devices, preferably optoelectronic devices. The current blocking structure comprises a semiconductor material arrangement comprising an n-type ruthenium doped indium phosphide (Ru—InP) layer and a first p-type semiconductor material layer wherein the n-type Ru—InP layer is less than 0.6 ?m thick. The semiconductor material arrangement and p-type semiconductor material layer form a current blocking p-n junction. The current blocking structure may further comprise other n-type layers and/or multiple n-type Ru—InP layers and/or intrinsic/undoped layers wherein the n-type Ru—InP layers may be thicker than 0.6 ?m.

Abstract: An optical amplifier has a low polarization dependent gain. The amplifier includes a gain medium including a plurality of adjoining semiconductor layers to provide optical gain wherein the adjoining semiconductor layers define one or more quantum wells for electrons and are operative to provide both direct and indirect electron-hole transitions in the gain medium. A first quantized electron energy level in the conduction band and a first quantized hole energy level in the valence band is located in a first layer. A further first quantized hole energy level in the valence band is located in an adjacent second layer.

Abstract: A hybrid integrated tuneable optical laser device, suitable for tuning to different wavelengths via a piezo micromotor (6) controlled optical filter (4) in an external cavity. Once the laser is fixed at a selected wavelength, no power is required to be applied to the wavelength tuning element to maintain the wavelength stability.

Abstract: A method for generating an optical single sideband signal comprising the steps of splitting an optical field into two parts and introducing a relative phase delay of +/??/4 radians in each direction of transmission to one of the parts, intensity reflection-modulating each part with electrical signals having a relative phase delay of +/??/2 radians and then recombining the reflection-modulated signals.

Abstract: An optical fibre network comprises a laser source (1a) configured to generate laser light of a plurality of wavelengths. A first optical fibre (4a), transmits multi-wavelength light from the laser source to a location remote from the laser source. A wavelength division multiplexer (2) at the remote location (203) is connected to a plurality of second optical fibres (8). A plurality of optical modulators (9) are each connected optically to the wavelength division multiplexer (2) via a respective second optical fibre (8). The wavelength division multiplexer (2) is arranged to de-multiplex the multi-wavelength light received from the first optical fibre (4a) into a plurality of wavelengths and to supply a respective wavelength to each of the second optical fibres (8). The optical modulators (9) are reflective optical modulators each arranged to modulate light received from the associated second optical fibre (8) with a data signal and to reflect the modulated light back along the second optical fibre (8).

Abstract: An electroabsorption modulator comprises an absorption layer, at least one layer of p-doped semiconductor, and at least one layer of n-doped semiconductor, said absorption layer being provided between said at least one layer of p-doped semiconductor and said at least one layer of n-doped semiconductor, and said layers forming a ridge waveguide structure, wherein the thickness of said absorption layer is between 9 and 60 nm, the width of said absorption layer is between 4.5 and 12 microns, and the width of at least one of said at least one layer of p-doped semiconductor and said at least one layer of n-doped semiconductor is between 4.5 and 12 microns; whereby the width of said ridge waveguide structure is between 4.5 and 12 microns.

Abstract: A method of fabricating a photonic device comprises the steps of providing a core pattern of waveguide core material (1) on a base layer (3) and applying a cladding layer (2) over the core material 1 and the base layer (3). The height of the surface of the cladding layer (2) over the base layer (3) varies in dependence on the pattern of core material (1). The core pattern is designed with at least two reference regions, each having a width w that is selected to provide a peak of the cladding layer (2) with a predetermined height h1 over each reference region. The core pattern is further designed such that a line between the peaks of the reference regions is higher than any intervening peaks of the cladding layer, whereby the peaks of the reference regions provide a vertical alignment reference.

Abstract: An optical device for generating a beat frequency between two optical wavelengths includes two waveguides (2a, 2b) of different width and a grating layer (4) that is common to both wave guides.

Abstract: A detector for electromagnetic radiation in the range 80 GHz to 4 THz comprises a laser light source (115) an optical modulator (13) arranged to modulate light from the laser light source (11) and a filter system (17) for selecting a defined range of frequencies of the modulated light. The optical modulator is an electroabsorption modulator (13) with an antenna (15) which is sensitive to electromagnetic radiation in the range 80 GHz to 4 THz. The signal received by the antenna (15) modulates the electric field across the electroabsorption modulator (13), whereby to modulate the light from the laser light source (11).

Abstract: An optoelectronic device has at least a first facet (S), a first waveguide (2) and a second waveguide (3). The waveguides are substantially coincident at the first facet (6), such that light travelling along the first waveguide (2) is reflected into the second waveguide (3) by the first facet (6). The first facet (6) is formed by precision cleaving. Preferably an etch feature is incorporated in the same mask level as that to define the waveguide core.

Abstract: An optical device for generating a beat frequency between two optical wavelengths includes two waveguides (2a, 2b) of different width and a grating layer (4) that is common to both wave guides.