Method and system for ultra-high bit rate fiber-optic communications
View Patent ↗A method and system for ultra-high bit rate fiber-optic communications (e.g., 160 Gb/s) utilize a phase-correlated modulation format where phases of bits in adjacent four-bit groups in transmitted optical pulse trains are altered by π (or 180°).
1. A method of synchronizing a receiver in an ultra-high bit rate fiber-optic communications network, comprising:
modulating a coherent continuous-wave (CW) laser to form a phase-correlated optical data stream comprising a sequence of four-bit groups, wherein adjacent four-bit groups have respective phase relationships offset by π; and
transmitting the phase-correlated optical data stream, wherein the phase-correlated optical data stream is adapted to be filtered at the receiver using an optical band-pass filter to recover thereby a clock signal wherein the optical band-pass filter has a bandwidth of about ¼ of a bandwidth of the modulated optical signal of the CW laser.
2. The method of claim 1 , further comprises:
modulating a pump laser with a data pattern stream where a state of polarization of adjacent four-bit groups is altered.
3. The method of claim 2 , further comprises:
modulating the pump laser at a bit rate of about 160 Gb/s.
4. The method of claim 2 , wherein the state of polarization of the adjacent four-bit groups is altered by π/2.
5. The method of claim 2 , wherein the coherent CW laser is modulated using a fiber-based Kerr-effect shutter controlled by a modulated output signal of the pump laser.
6. The method of claim 1 , wherein the method further comprises:
using an electro-optical converter comprising a Mach-Zehnder modulator and a controlled polarizer for converting data to be transmitted.
7. An apparatus for synchronizing a receiver in an ultra-high bit rate fiber-optic communications network, comprising:
means for modulating a coherent continuous-wave (CW) laser to form a phase-correlated optical data stream comprising a sequence of four-bit groups, wherein adjacent four-bit groups have respective phase relationships offset by π; and
means for transmitting the phase-correlated optical data stream, wherein the phase-correlated optical data stream is adapted to be filtered at the receiver using an optical band-pass filter to recover thereby a clock signal wherein the coherent CW laser is modulated using a fiber-based Kerr-effect shutter controlled by a modulated output signal of the pump laser.
8. The apparatus of claim 7 , further comprises:
means for modulating a pump laser with a data pattern stream where a state of polarization of adjacent four-bit groups is altered.
9. The apparatus of claim 8 , wherein the pump laser is modulated at a bit rate of about 160 Gb/s.
10. The method of claim 8 , wherein the state of polarization of the adjacent four-bit groups is altered by π/2.
11. The method of claim 9 , wherein the transmitting means comprises:
a Mach-Zehnder modulator and a controlled polarizer for converting data to be transmitted.
12. A wavelength division multiplexing (WDM) system for ultra-high bit rate fiber-optic communications, comprising:
a wavelength-matched transmitter at a first terminal comprises:
a pump laser;
an electro-optical converter for converting of data to be transmitted from the first terminal to a second terminal, the electro-optical converter including a modulator of a pump laser beam;
a coherent continuous-wave (CW) laser; and
a Kerr-effect shutter for producing, from the coherent beam of the CW laser, a phase-correlated optical data stream comprising a sequence of four-bit groups, whereby adjacent four-bit groups have respective phase relationships offset by π, wherein the shutter is controlled by a modulated signal of the pump laser;
a fiber-optic span propagating the phase-correlated data stream between the wavelength-matched transmitter of the first terminal with a wavelength-matched receiver of a second terminal; and
the wavelength-matched receiver for receiving the phase-correlated data stream comprises:
an opto-electronic demodulator for demodulating the phase correlated data stream; and
a synchronization circuit for recovering a clock signal.
13. The system of claim 12 wherein the modulator modulates the pump laser at an ultra-high bit rate.
14. The system of claim 12 wherein the CW laser is modulated to form a phase-correlated optical pulse train where phases of bits in adjacent four-bit groups are altered by π.
15. The system of claim 12 wherein the modulator uses on/off keying modulation scheme.
16. The system of claim 12 wherein the synchronization circuit further comprises an optical band-pass filter and an electrical band-pass filter, wherein a bandwidth of the optical band-pass filter is about ¼ of a bandwidth of the modulated optical signal of the CW laser.
17. The system of claim 16 wherein a Q-factor of the electrical band-pass filter is greater than or equal to 1000.
18. The system of claim 16 wherein a central frequency of the electrical band-pass filter is about ¼ of the ultra-high bit rate.