Method and arrangement for transmitting power in optical form over optical fibres

Claim 1

A power transmission arrangement in which operating power for a remote device is conveyed as light, the arrangement comprising a power generation station for generating optical power, a remote power consuming station separated from said power generation station, and optical fibre means coupling the power generation station to the power consuming station for conveying said optical power thereto, said optical fibre means comprising a long wavelength multimode first optical fibre having a relatively thick core size in the range 50 to 400 μm, the power generation station including a plurality of high-power gas or solid-state laser or superluminescent diodes, each having an optical output with a wavelength of the order of 0.70 to 1.7 μm and each feeding light energy into a respective second length of multimode optical fibre, and means for inputting the optical power output of the power generation station into one end of the said optical fibre means, said inputting means comprising an optical coupler coupled to the respective second lengths of multimode optical fibre from said plurality of lasers or diodes and to one end of the first optical fibre, wherein the remote power consuming station includes a photo-responsive detector upon which the optical power conveyed thereto and output from another end of the optical fibre means falls, and a utilization device coupled to the detector for utilizing said power, and wherein the detector includes a layered structure of the following layers: (i) a first relatively thick layer of the order of 200 μm of indium phosphide doped to have an n - semi-insulating characteristic for receiving optical energy being directed to this layer, (ii) a front contact which has a thickness in the range of 2 to 4 μm of LPE indium phosphide of n + type and a doping of the order of 10 18 -10 19 cm -3 disposed on the first layer, (iii) a metallization on said front contact layer on an opposite face from the first layer for providing one contact for the extraction of electrical energy, which metallization covers a relatively small part of the opposite face, (iv) a buffer layer also on the said opposite face of the front contact layer, which buffer layer has a thickness of the order of 1 μm, and is of LPE indium phosphide, n - type doping of the order of 10 16 cm -3 , (v) a layer of LPE indium gallium arsenide, n - type doping of the order of 10 16 cm -3 , which layer has a thickness of the order of 3 μm, (vi) another layer of LPE indium gallium arsenide having a thickness of the order to 5 μm and being p + type doping of the order of 10 18 cm -3 , and (vii) a titanium gold alloy metallization on the outer face of the layer of p + type indium gallium arsenide, which metallization provides another contact for the extraction of electrical energy.