Coherent optical receiver

A coherent optical receiver that receives an optical PSK-modulated signal, the coherent optical receiver comprising:

• a first optical hybrid coupler configured to receive the optical PSK-modulated signal and produce first and second output signals that have a predefined phase offset relative to one another, wherein the optical PSK-modulated signal employs a plurality of phases greater than two;
• first and second waveguides (603A and 603B) coupled to the first optical hybrid coupler for receiving the first and second output signals, respectively;
• a second optical hybrid coupler configured to receive an optical local-oscillating (LO) signal and produce third and fourth output signals that have a predefined phase offset relative to one another;
• third and fourth waveguides (603C and 603D) coupled to the second optical hybrid coupler for receiving the third and fourth output signals, respectively;
• a first optical mixer-detector, coupled to the first and third waveguides (603A and 603C), the first optical mixer-detector configured to:
• (i) receive the first and third output signals,
• (ii) mix the first and third output signals to produce first and second coupled signals, and
• (iii) split the first coupled signal into first and second split signals, and the second coupled signal into third and fourth split signals, wherein the first and second split signals have a predefined phase offset relative to one another, and the third and fourth split signals have a predefined phase offset relative to one another;
• a second optical mixer-detector, coupled to the second and fourth waveguides (603B and 603D), the second optical mixer-detector configured to:
• (i) receive the second and fourth output signals,
• (ii) mix the second and fourth output signals to produce third and fourth coupled signals, and
• (iii) split the third coupled signal into fifth and sixth split signals, and the fourth coupled signal into seventh and eighth split signals, wherein the fifth and sixth split signals have a predefined phase offset relative to one another, and the seventh and eighth split signals have a predefined phase offset relative to one another;
• first and second thyristors;
• a first control circuit operably coupled to the first thyristor, and coupled to the first optical mixer-detector for receiving the first through fourth split signals, wherein the first control circuit controls a switching operation of the first thyristor, and wherein the first thyristor to produces a first set of digital output signals;
• and
• a second control circuit operably coupled to the second thyristor, and coupled to the second optical mixer-detector for receiving the fifth through eighth split signals, wherein the second control circuit controls a switching operation of the second thyristor, wherein the second thyristor produces a second set of digital output signals, and wherein binary levels of signals in each of the first and second sets of digital output signals correspond to phase offsets of the optical PSK-modulated signal.