Clock recovery and equalizer estimation in a multi-channel receiver
A multi-channel receiver that includes a first clock recovery unit configured to recover a first clock signal associated with a first optical channel is disclosed. A first coefficient estimation unit estimates a first set of coefficients using the first clock signal. A second clock recovery unit configured to recover a second clock signal associated with a second optical channel using the first clock signal as a reference clock signal. A second coefficient estimation unit estimates a second set of coefficients using the first set of coefficients.
1. A multi-channel receiver comprising:
a second clock recovery unit configured to recover a second clock signal associated with a second channel, the second clock recovery unit being configured to use a first clock signal that is associated with a first channel as a reference clock signal; and
a second coefficient estimation unit configured to estimate a second set of coefficients using a first set of coefficients as first initialization coefficients,
wherein:
the first set of coefficients is estimated using the first clock signal and is configured for use to equalize the first channel, and
the second set of coefficients is suitable for use by an equalizer circuit associated with the second channel.
2. The multi-channel receiver of claim 1 , 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; and
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.
3. The multi-channel receiver of claim 2 , further comprising the third clock recovery unit that is configured to:
recover a third clock signal associated with the third channel using the second clock signal as a reference clock signal; and
pass the third clock signal from the third clock recovery unit to a fourth clock recovery unit associated with a fourth channel.
4. The multi-channel receiver of claim 3 , 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.
5. The multi-channel receiver of claim 3 , 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.
6. The multi-channel receiver of claim 1 , wherein a channel spacing between the first channel and the second channel is within a range between 15 nanometers (nm) and 60 nm.
7. The multi-channel receiver of claim 1 , wherein the first clock signal is recovered using a first clock recovery unit and is passed from the first clock recovery unit to the second clock recovery unit.
8. The multi-channel receiver of claim 1 , wherein the first set of coefficients are estimated at a first coefficient estimation unit and passed to the second coefficient estimation unit.
9. The multi-channel receiver of claim 1 , further comprising:
a first clock recovery unit that is configured to recover the first clock signal and to pass the first clock signal to the second clock recovery unit; and
a first coefficient estimation unit that is configured to estimate the first set of coefficients using the first clock signal.
10. The multi-channel receiver of claim 1 , further 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;
the first clock recovery unit is configured to receive a first optical carrier signal of the optical carrier signals from the DEMUX and to recover the first clock signal from the first optical carrier signal; and
the second clock recovery unit is configured to receive a second optical carrier signal of the optical carrier signals from the DEMUX, to receive the first clock signal from the first clock recover unit, and to recover the second clock signal using the first clock signal.
11. The multi-channel receiver of claim 10 , wherein:
the first optical carrier signal is associated with a first wavelength;
the second optical carrier signal is associated with a second wavelength; and
the first wavelength is between the second wavelength and the particular wavelength.
12. The multi-channel receiver of claim 1 , 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.
13. A receiver processing module of a receiver, the receiver processing module comprising:
a second receiver processing unit;
a first receiver processing unit that is configured to receive a first optical carrier signal on a first channel of two or more optical carrier signals, the first receiving processing unit being configured to:
recover a first clock signal associated with the first channel;
estimate a first set of coefficients using the first clock signal,
equalize the first optical carrier signal using the first set of coefficients; and
pass the first clock signal and the first set of coefficients to the second receiver processing unit,
wherein the second receiver processing unit is configured to:
receive a second optical carrier signal on a second channel of the two or more optical carrier signals,
using the first clock signal, recover a second clock signal associated with the second channel as a reference clock signal;
initialize a second set of coefficients using the first set of coefficients;
estimate a second set of coefficients using an equalization scheme after initialziation;
equalize the second optical carrier signal using the second set of coefficients; and
pass the second clock signal and the second set of coefficients to a third receiver processing unit.
14. The receiver processing module of claim 13 , further comprising the third receiver processing unit and a fourth receiver processing unit, wherein:
the third receiver processing unit is configured to receive a third optical carrier signal on a third channel of the two or more optical carrier signals, recover a third clock signal associated with the third channel as a reference clock signal using the second clock signal; estimate a third set of coefficients using the second set of coefficients as first initialization coefficients, equalize the third optical carrier signal using the third set of coefficients; and pass the third clock signal and the third set of coefficients to the fourth receiver processing unit; and
the fourth receiver processing unit is configured to receive a fourth optical carrier signal on a fourth channel of the two or more optical carrier signals, recover a fourth clock signal associated with the fourth channel as a reference clock signal using the third clock signal; estimate a fourth set of coefficients using the third set of coefficients as first initialization coefficients, and equalize the fourth optical carrier signal using the fourth set of coefficients.
15. The receiver processing module of claim 14 , wherein the first receiver processing unit, the second receiver processing unit, the third receiver processing unit, and the fourth receiver processing unit each include a clock recovery unit, an equalizer, and a coefficient estimation unit.
16. The receiver processing module of claim 15 , wherein the two or more optical carrier signals are in a wavelength range between about 780 nanometers (nm) and 1000 nm.
17. The receiver processing module 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 processing module 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. The receiver of claim 13 , wherein the first channel has a first channel response that is related to a second channel response of the second channel.
20. The receiver of claim 13 , 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.