Coherent optical receivers
First Claim
1. A method of producing a local oscillator (LO) optical signal for combination with an incoming optical signal to be received by a coherent optical receiver, comprising the steps of:
- producing an optical signal having a first optical component having a first frequency and a second optical component having a frequency offset from the first frequency by a second frequency;
controlling the first frequency with a first control signal having a relatively slow response speed and dependent upon relative frequency changes between the LO optical signal and the incoming optical signal;
producing an electrical signal at a frequency harmonically related to the second frequency;
controlling the frequency of the electrical signal, thereby to control the second frequency, with a second control signal having a relatively fast response speed and dependent upon relative phase changes between the LO optical signal and the incoming optical signal; and
deriving the LO optical signal from said second optical component.
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Accused Products
Abstract
In a coherent optical receiver, an incoming optical signal is combined with a local oscillator (LO) optical signal and the combined optical signals are detected by an optical detector and receiver arrangement. The receiver produces first and second loop control signals having respectively relatively slow and fast response speeds dependent upon frequency and phase variations between the incoming signal and the LO signal. An electrical source produces an electrical signal having a GHz frequency controlled by the second control signal. An optical source produces an optical signal with a first component having a first frequency controlled by the first control signal, and a second component having a frequency offset from the first frequency by a second frequency dependent upon the frequency of the electrical signal. The LO signal is derived from the second optical component via an optical filter and amplifier. The optical source can comprise a laser and an optical amplitude or phase modulator, or a dual- or multiple-frequency laser.
100 Citations
27 Claims
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1. A method of producing a local oscillator (LO) optical signal for combination with an incoming optical signal to be received by a coherent optical receiver, comprising the steps of:
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producing an optical signal having a first optical component having a first frequency and a second optical component having a frequency offset from the first frequency by a second frequency;
controlling the first frequency with a first control signal having a relatively slow response speed and dependent upon relative frequency changes between the LO optical signal and the incoming optical signal;
producing an electrical signal at a frequency harmonically related to the second frequency;
controlling the frequency of the electrical signal, thereby to control the second frequency, with a second control signal having a relatively fast response speed and dependent upon relative phase changes between the LO optical signal and the incoming optical signal; and
deriving the LO optical signal from said second optical component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A coherent optical receiver comprising:
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an optical coupler for combining an incoming optical signal to be received with a local oscillator (LO) optical signal to produce at least one combined optical signal;
an optical detector and receiver arrangement responsive to the combined optical signal to produce a coherent output signal and two loop control signals having relatively slow and fast response speeds and dependent upon frequency and phase variations between the incoming optical signal and the LO optical signal;
an electrical signal source;
an optical signal generator arranged to produce an optical signal comprising a first optical component at a first frequency controlled by the first control signal and a second optical component at a frequency which is offset from the first frequency by a second frequency, said second frequency being dependent upon a frequency of an electrical signal produced by the electrical signal source and being controlled by the second control signal; and
means for deriving the LO optical signal from said second optical component of the optical signal produced by the optical signal generator. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A coherent optical receiver comprising:
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an optical signal combiner arranged to combine an incoming optical signal to be received with a local oscillator (LO) optical signal to produce at least one combined optical signal;
an optical detector and receiver arrangement responsive to said at least one combined optical signal to produce a coherently received signal and two loop control signals having relatively slow and fast response speeds dependent upon frequency and phase variations between the incoming optical signal and the LO optical signal;
an electrical source for producing an electrical signal having a frequency controlled by the control signal having the relatively fast response speed; and
an optical source for producing an optical signal comprising a first optical signal component having a first frequency controlled by the control signal having the relatively slow response speed and a second optical signal component having a frequency offset from the first frequency by a second frequency harmonically related to the frequency of the electrical signal, wherein the LO optical signal is derived from the second optical signal component. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification