OPTICAL COUPLER WITH STABILIZED COUPLING RATIO

An optical coupler is provided, which includes at least one first-type delay part having a delay quantity; at least one second-type delay part having a basic delay quantity and an adjustable delay quantity; and a plurality of optical splitting units. The plurality of optical splitting units is connected to the first-type delay part and the second-type delay part between an input end and an output end, for example, connected in a cascade manner, so as to obtain a stable effective coupling ratio. Alternatively, any desired stable effective coupling ratio may also be obtained by a set of the adjustable delay quantity.