US 11,949,461 B1
Integrated self-coherent receiving optical chip based on round-trip delay interferometers
Yibo Zhao, Beijing (CN); Dong Wang, Beijing (CN); and Dongsheng Chen, Beijing (CN)
Assigned to BEIJING ZHONGKE GUOGUANG QUANTUM TECHNOLOGY CO., LTD., Beijing (CN)
Filed by BEIJING ZHONGKE GUOGUANG QUANTUM TECHNOLOGY CO., LTD., Beijing (CN)
Filed on Jun. 19, 2023, as Appl. No. 18/211,346.
Claims priority of application No. 202211036839.1 (CN), filed on Aug. 29, 2022.
Int. Cl. H04B 10/61 (2013.01)
CPC H04B 10/6151 (2013.01) [H04B 10/614 (2013.01); H04B 10/616 (2013.01)] 8 Claims
OG exemplary drawing
 
1. An integrated self-coherent receiving optical chip based on round-trip delay interferometers, comprising: a first beam splitter, a multi-port circulator array, a first round-trip delay interferometer and a second round-trip delay interferometer, which are integrated on a same substrate, wherein,
the first beam splitter is configured to split a signal light input to a first port of the integrated self-coherent receiving optical chip to generate a first signal light component and a second signal light component;
the multi-port circulator array is configured to transmit the first signal light component input to a first port of the multi-port circulator array to a second port of the multi-port circulator array to be output; and transmit the second signal light component input to a fourth port of the multi-port circulator array to a fifth port of the multi-port circulator array to be output;
the first round-trip delay interferometer has a first long arm and a first short arm, the first long arm and the first short arm are configured to perform a round-trip transmission of the first signal light component input to a first port of the first round-trip delay interferometer, and perform a delayed self-interference before returning to the first port of the first round-trip delay interferometer, to generate a first interference optical signal and a second interference optical signal to be output from the first port of the first round-trip delay interferometer and a second port of the first round-trip delay interferometer respectively;
the second round-trip delay interferometer has a second long arm and a second short arm, a phase difference between the second long arm and the second short arm is π/2, and the second long arm and the second short arm are configured to perform a round-trip transmission of the second signal light component input to a first port of the second round-trip delay interferometer, and perform a delayed self-interference before returning to the first port of the second round-trip delay interferometer, to generate a third interference optical signal and a fourth interference optical signal to be output from the first port of the second round-trip delay interferometer and a second port of the second round-trip delay interferometer respectively;
the multi-port circulator array is further configured to transmit the first interference optical signal input to the second port of the multi-port circulator array to a third port of the multi-port circulator array, and output the first interference optical signal from a second port of the integrated self-coherent receiving optical chip; and transmit the third interference optical signal input to the fifth port of the multi-port circulator array to a sixth port of the multi-port circulator array, and output the third interference optical signal from a fourth port of the integrated self-coherent receiving optical chip;
the multi-port circulator array comprises a first polarization beam splitting rotator, a first optical waveguide, a second optical waveguide, a second polarization beam splitting rotator, a third polarization beam splitting rotator, a third optical waveguide, a fourth optical waveguide, a fourth polarization beam splitting rotator and non-reciprocal polarization rotation modules,
each of the first optical waveguide, the second optical waveguide, the third optical waveguide, and the fourth optical waveguide comprises one of the non-reciprocal polarization rotation modules; each of the non-reciprocal polarization rotation modules is configured to rotate a polarization state of an optical signal passing from one direction by 90° and keep a polarization state of an optical signal passing from other direction unchanged;
the first polarization beam splitting rotator is configured to perform a polarization beam splitting on the first signal light component input to one input port of the first polarization beam splitting rotator to generate a first polarization component and a second polarization component of the first signal light component;
the second polarization beam splitting rotator is configured to perform a polarization beam combining on the first polarization component and the second polarization component of the first signal light component passing through the non-reciprocal polarization rotation modules in a forward direction, to recombine the first polarization component and the second polarization component of the first signal light component into the first signal light component; and configured to perform a polarization beam splitting on the first interference optical signal to generate a first polarization component and a second polarization component of the first interference optical signal;
the first polarization beam splitting rotator is further configured to perform a polarization beam combining on the first polarization component and the second polarization component of the first interference optical signal passing through the non-reciprocal polarization rotation modules in a reverse direction, to recombine the first polarization component and the second polarization component of the first interference optical signal into the first interference optical signal to be output from another input port of the first polarization beam splitting rotator;
the third polarization beam splitting rotator is configured to perform a polarization beam splitting on the second signal light component input to one input port of the third polarization beam splitting rotator to generate a first polarization component and a second polarization component of the second signal light component;
the fourth polarization beam splitting rotator is configured to perform a polarization beam combining on the first polarization component and the second polarization component of the second signal light component passing through the non-reciprocal polarization rotation modules in the forward direction, to recombine the first polarization component and the second polarization component of the second signal light component into the second signal light component; and perform a polarization beam splitting on the third interference optical signal to generate a first polarization component and a second polarization component of the third interference optical signal;
the third polarization beam splitting rotator is further configured to perform a polarization beam combining on the first polarization component and the second polarization component of the third interference optical signal passing through the non-reciprocal polarization rotation modules in the reverse direction, to recombine the first polarization component and the second polarization component of the third interference optical signal into the third interference optical signal to be output from another input port of the third polarization beam splitting rotator; and wherein, the signal light E(t) received by the integrated self-coherent receiving optical chip first enters the first beam splitter to be split into the first signal light component E1(t) and the second signal light component E2(t), which satisfy E1(t)=E2(t)=1/√2E(t), wherein the first signal light component enters the first port of the multi-port circulator array, is output from the second port of the multi-port circulator array, reaches the first port of the first round-trip delay interferometer for the round-trip transmission, and completes the delayed self-interference before returning to the first port of the first round-trip delay interferometer, to generate to the first interference optical signal Eout1(t) and the second interference optical signal Eout2(t), which are respectively expressed as:

OG Complex Work Unit Math
wherein τ refers to a delay corresponding to an arm length difference between a long arm and a short arm of a first polarization-independent delay interferometer;
the first interference optical signal is output from the first port of the first round-trip delay interferometer into which the first signal light component enters, enters the second port of the multi-port circulator array, is output from the third port of the multi-port circulator array, and is output from the second port of the integrated self-coherent receiving optical chip; the second interference optical signal is output from the second port of the first round-trip delay interferometer, and is output from a third port of the integrated self-coherent receiving optical chip;
a differential current signal is generated by performing a balanced detection on the first interference optical signal and the second interference optical signal respectively output from the second port of the integrated self-coherent receiving optical chip and the third port of the integrated self-coherent receiving optical chip, which is an in-phase component and is expressed as:

OG Complex Work Unit Math
wherein R refers to a response efficiency of a photoelectric detector, ω refers to an angular frequency of the signal light;
the second signal light component enters the fourth port of the multi-port circulator array, is output from the second port of the multi-port circulator array and reaches the first port of the second round-trip delay interferometer for the round-trip transmission, and completes delay self-interference before returning to the first port of the second round-trip delay interferometer; with the phase difference π/2 between the second long arm and the second short arm of the second round-trip delay interferometer, the third interference optical signal Eout3 (t) and the fourth interference optical signal Eout4 (t) are respectively expressed as:

OG Complex Work Unit Math
wherein τ refers to a delay corresponding to an arm length difference between a long arm and a short arm of a second polarization-independent delay interferometer,
the third interference optical signal is output from the first port of the second round-trip delay interferometer into which the second signal light component enters, enters the fifth port of the multi-port circulator array, and is output from the sixth port of the multi-port circulator array, and is output from the fourth port of the integrated self-coherent receiving optical chip; the fourth interference optical signal is output from the second port of the second round-trip delay interferometer, and is output from a fifth port of the integrated self-coherent receiving optical chip,
a second differential current signal is generated by performing the balanced detection on the third interference optical signal and the fourth interference optical signal respectively output from the fourth port of the integrated self-coherent receiving optical chip and the fifth port of the integrated self-coherent receiving optical chip, which is a quadrature phase component and is expressed as:

OG Complex Work Unit Math
an electrical signal of the in-phase component and an electrical signal of the quadrature phase component are synthesized into a complex signal, which is expressed as:

OG Complex Work Unit Math
the complex signal is sampled and digitized to recover electric field information of the signal light and obtain service data.