OPTICAL IQ MODULATOR
An optical IQ modulator ( 10 ) comprising•a modulator input port ( 11 );•a modulator output port ( 12 );•a plurality of optical branches ( 13 ) connected in parallel therebetween;•each optical branch ( 13 ) comprising an optical interferometer ( 1 ), each optical interferometer ( 1 ) comprising•an optical splitter ( 2 );•an optical combiner ( 3 ); and,•a plurality of optical paths ( 4 ) connected therebetween:•at least one electrode ( 7 ) arranged in close proximity to an optical path ( 4 ) for altering the phase of an optical signal passing along the path ( 4 );•the optical splitter ( 2 ) being in being in optical communication with the modulator input port ( 11 ) and being adapted to split light received from the modulator input port ( 11 ) into the plurality of optical paths ( 4 );•the optical combiner ( 3 ) having an optical output port ( 5 ) in optical communication with the modulator output port ( 12 ), the optical combiner ( 3 ) being adapted to combine the optical signals from the plurality of optical paths ( 4 ) at the output port ( 5 );•at least one optical interferometer ( 1 ) comprising an optical tap ( 8 ) adapted to receive and combine the optical signals from the plurality of optical paths ( 4 ) in a different phase relation to the combination at the output port ( 5 ) of the interferometer combiner ( 3 ).
1 . An optical IQ modulator comprising:
a modulator input port;
a modulator output port; and
a plurality of optical branches connected in parallel between the modulator input and output ports;
each optical branch comprising an optical interferometer, each optical interferometer comprising:
an optical splitter;
an optical combiner;
a plurality of optical paths connected between the optical splitter and combiner; and
at least one electrode arranged in close proximity to at least one of the plurality of optical paths for altering the phase of an optical signal passing along the at least one of the plurality of optical paths;
the optical splitter being in optical communication with the modulator input port and being adapted to split light received from the modulator input port into the plurality of optical paths;
the optical combiner having an optical output port in optical communication with the modulator output port, the optical combiner being adapted to combine optical signals from the plurality of optical paths at the optical output port;
at least one of the optical interferometers comprising an optical tap adapted to receive and combine the optical signals from the plurality of optical paths in a different phase relation to the combined optical signals at the output port of the optical combiner.
2 . An optical IQ modulator as claimed in claim 1 , wherein the optical tap is adapted such that an output from the optical tap is a minimum when an output from the output port of the optical combiner is a maximum.
3 . An optical IQ modulator as claimed in claim 1 , further comprising an optical signal measurement means connected to the optical tap.
4 . An optical IQ modulator as claimed in claim 3 , wherein the optical signal measurement means measures an amplitude of the optical signal at the optical tap.
5 . An optical IQ modulator as claimed in claim 3 , wherein the optical measurement means measures an intensity of the optical signal at the optical tap.
6 . An optical IQ modulator as claimed in claim 1 , wherein each optical interferometer comprises the optical tap.
7 . An optical IQ modulator as claimed in claims 1 , wherein the at least one of the optical interferometers has the at least one electrode in close proximity to each of the plurality of optical paths.
8 . An optical IQ modulator as claimed in claim 7 , wherein each optical interferometer has the at least one electrode in close proximity to each of the plurality of optical paths.
9 . An optical IQ modulator as claimed in claim 1 , further comprising a voltage source connected to the at least one electrode.
10 . An optical IQ modulator as claimed in claim 1 , further comprising a coherent optical source connected to the modulator input port.
11 . An optical IQ modulator as claimed in claim 1 , further comprising a phase shifter arranged between the output port of the optical combiner and the modulator output port.
12 . An optical IQ modulator as claimed in claim 1 , wherein the IQ modulator comprises two branches, each branch comprising at least one of the optical interferometers.
13 . An optical IQ modulator as claimed in claim 1 , wherein each optical interferometer comprises two optical paths.
14 . (canceled)
15 . The optical IQ modulator as claimed in claim 10 , wherein the coherent optical source is a continuous wave laser.
16 . The optical IQ modulator as claimed in claim 11 , wherein the phase shifter is a 90 degree phase shifter.