Optical equalizer

DETAILED DESCRIPTION It is an object of the present invention to provide an easily scalable optical equalisation to at least partially compensate for the effects of gain tilt in optical amplifiers.
It is a further object of the present invention to provide an adaptive optical equaliser using planar waveguide technology, without the fabrication problems of prior art devices.
According to a first aspect of the present invention there is provided an optical equaliser comprising a plurality of serially concatenated filter elements the phase and modulation depth of which can be individually tuned, the filter elements being tunable in order to generate a desired optical equalisation function.
Preferably, each filter element is a three arm interferometer.
Preferably, the filter elements are fabricated utilising integrated waveguide technology.
According to a second aspect of the present invention there is provided a method of optical equalisation of an optical signal, for use in an optical communications system, comprising the steps of: filtering the optical signal transmitted by said optical element in the optical communications system through a plurality of serially concatenated, variable modulation depth and variable phase, periodic filters elements, and tuning the filter elements in order to generate a desired optical equalisation function.
Preferably, the individual filter elements are distributed at remote locations within a device the optical output of which is to be equalised.
Preferably, individual filter elements can be added to the equaliser to improve the gain flattened produced by the equaliser.
According to a further aspect of the present invention there is provided an optical amplifier including an amplifying element and an optical equaliser comprising a plurality of serially concatenated, variable phase, variable modulation depth, periodic filters each of which is tunable in order to optimise the optical equalisation of an optical signal transmitted by said amplifying element.
Preferably, individual filter elements are distributed at remote locations within the amplifier