Clock recovery and equalizer estimation in a multi-channel receiver
View Patent ↗A method of performing clock recovery and equalizer coefficient estimation in a multi-channel receiver may include recovering, at a first clock recovery unit, a first clock signal associated with a first channel. The method may include estimating a first set of coefficients for a first equalizer associated with the first channel using the first clock signal. The method may include passing the first clock signal to a second clock recovery unit associated with a second channel. The method may also include recovering, at the second clock recovery unit, a second clock signal associated with the second channel using the first clock signal as a reference clock signal. The method may also include passing the first set of coefficients as initialization coefficients to a second equalizer associated with the second channel. The method may also include estimating a second set of coefficients for the second equalizer using the initialization coefficients.
1. A method of performing clock recovery and equalizer coefficient estimation in a multi-channel receiver, the method comprising:
recovering, at a first clock recovery unit, a first clock signal associated with a first channel;
estimating a first set of coefficients for a first equalizer associated with the first channel using the first clock signal;
passing the first clock signal from the first clock recovery unit to a second clock recovery unit associated with a second channel;
recovering, at the second clock recovery unit, a second clock signal associated with the second channel using the first clock signal as a reference clock signal to the second clock recovery unit;
passing the first set of coefficients as first initialization coefficients to a second equalizer associated with the second channel; and
estimating a second set of coefficients for the second equalizer using the first initialization coefficients.
2. The method of claim 1 , wherein estimating the second set of coefficients for the second equalizer comprises:
initializing the second set of coefficients using the first initialization coefficients; and
estimating the second set of coefficients using an equalization scheme after the initialization.
3. The method of claim 1 , wherein the first channel includes a first channel response that is related to a second channel response of the second channel.
4. The method of claim 1 , wherein:
the first channel is associated with a wavelength for which an optical link is optimized; and
the first channel has a smaller inter-symbol interference (ISI) than the second channel.
5. The method of claim 4 , wherein the optical link includes a multi-mode fiber (MMF) link.
6. The method of claim 1 , further comprising:
passing the second clock signal from the second clock recovery unit to a third clock recovery unit associated with a third channel;
recovering, at the third clock recovery unit, a third clock signal associated with the third channel using the second clock signal as a reference clock signal to the third clock recovery unit;
passing the second set of coefficients as second initialization coefficients to a third equalizer associated with the third channel;
estimating a third set of coefficients for the third equalizer based on the second initialization coefficients;
passing the third clock signal from the third clock recovery unit to a fourth clock recovery unit associated with a fourth channel;
recovering, at the fourth clock recovery unit, a fourth clock signal associated with the fourth channel using the third clock signal as a reference clock signal to the fourth clock recovery unit;
passing the third set of coefficients as third initialization coefficients to a fourth equalizer associated with the fourth channel; and
estimating a fourth set of coefficients for the fourth equalizer based on the third initialization coefficients.
7. The method of claim 6 , wherein:
the second channel is a neighbor channel of the first channel;
the third channel is a neighbor channel of the second channel; and
the fourth channel is a neighbor channel of the third channel.
8. The method of claim 7 , wherein:
the first channel is associated with a wavelength of 850 nanometers (nm);
the second channel is associated with a wavelength of 880 nm;
the third channel is associated with a wavelength of 910 nm; and
the fourth channel is associated with a wavelength of 940 nm.
9. The method of claim 6 , wherein:
the first channel is associated with a wavelength optimized for performance on an optical link and has a smaller inter-symbol interference (ISI) than the second channel;
the second channel has a smaller ISI than the third channel; and
the third channel has a smaller ISI than the fourth channel.
10. The method of claim 1 , wherein:
the first channel is associated with a first wavelength within a range between 800 nanometers (nm) and 1000 nm;
the second channel is associated with a second wavelength within the range between 800 nm and 1000 nm; and
a channel spacing between the first channel and the second channel is within a range between 15 nm and 60 nm.
11. A multi-channel receiver comprising:
a first clock recovery unit configured to recover a first clock signal associated with a first channel, the first clock recovery unit configured to pass the first clock signal to a second clock recovery unit associated with a second channel;
a first coefficient estimation unit configured to estimate a first set of coefficients for a first equalizer associated with the first channel using the first clock signal, the first coefficient estimation unit configured to pass the first set of coefficients to a second coefficient estimation unit;
the second clock recovery unit configured to recover a second clock signal associated with the second channel using the first clock signal as a reference clock signal to the second clock recovery unit; and
the second coefficient estimation unit configured to estimate a second set of coefficients for a second equalizer associated with the second channel using the first set of coefficients as first initialization coefficients for the second equalizer.
12. The receiver of claim 11 , wherein the second coefficient estimation unit is further configured to:
initialize the second set of coefficients using the first initialization coefficients; and
estimate the second set of coefficients using an equalization scheme after the initialization.
13. The receiver of claim 11 , wherein the first channel has a first channel response that is related to a second channel response of the second channel.
14. The receiver of claim 11 , wherein the first channel is associated with a wavelength for which an optical link is optimized and includes a smaller inter-symbol interference (ISI) than the second channel.
15. The receiver of claim 14 , wherein the optical link includes one of an OM3 fiber link and an OM4 fiber link.
16. The receiver of claim 11 , wherein:
the second clock recovery unit is further configured to pass the second clock signal from the second clock recovery unit to a third clock recovery unit associated with a third channel;
the second coefficient estimation unit is further configured to pass the second set of coefficients from the second coefficient estimation unit to a third coefficient estimation unit as second initialization coefficients; and
the receiver further comprises:
the third clock recovery unit configured to:
recover a third clock signal associated with the third channel using the second clock signal as a reference clock signal to the third clock recovery unit; and
pass the third clock signal from the third clock recovery unit to a fourth clock recovery unit associated with a fourth channel;
the third coefficient estimation unit configured to:
estimate a third set of coefficients for a third equalizer associated with the third channel using the second initialization coefficients; and
pass the third set of coefficients from the third coefficient estimation unit to a fourth coefficient estimation unit as third initialization coefficients;
the fourth clock recovery unit configured to recover a fourth clock signal associated with the fourth channel using the third clock signal as a reference clock signal to the fourth clock recovery unit; and
the fourth coefficient estimation unit configured to estimate a fourth set of coefficients for a fourth equalizer associated with the fourth channel using the third initialization coefficients.
17. The receiver of claim 16 , wherein:
the second channel is a neighbor channel of the first channel;
the third channel is a neighbor channel of the second channel; and
the fourth channel is a neighbor channel of the third channel.
18. The receiver of claim 17 , wherein:
the first channel is associated with a wavelength of 850 nanometers (nm);
the second channel is associated with a wavelength of 880 nm;
the third channel is associated with a wavelength of 910 nm; and
the fourth channel is associated with a wavelength of 940 nm.
19. A multi-channel receiver comprising:
a demultiplexer (DEMUX) that is configured to receive a laser beam from an optical link, wherein the optical link is optimized for a particular wavelength and the laser beam includes one or more optical carrier signals associated with other wavelengths;
a first clock recovery unit configured to receive a first optical carrier signal of the optical carrier signals from the DEMUX and to recover a first clock signal from the first optical carrier signal;
a second clock recovery unit configured to receive a second optical carrier signal of the optical carrier signals from the DEMUX, to receive a reference clock signal from the first clock recover unit, and to recover a second clock signal using the reference clock signal, wherein:
the first optical carrier signal is associated with a first wavelength;
the second optical carrier signal is associated with a second wavelength;
the first wavelength is between the second wavelength and the particular wavelength; and
the reference clock signal is the first clock signal; and
a first coefficient estimation unit configured to estimate a first set of coefficients for a first equalizer associated with the first channel using the first clock signal and pass the first set of coefficients as initialization coefficients to a second equalizer associated with the second clock recovery unit.