# US 8,090,268 B2 · Long-distance synchronous transmission method using optical fiber

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- Number: US 8,090,268 B2
- Document ID: US8090268B2
- Status: Granted
- Kind: B2
- Application number: 10/536,954
- Filed: 2003-10-15
- Published: 2006-03-16
- Granted: 2012-01-03
- Earliest claimed: 2002-12-02
- Assignees: Ekinops
- Inventors: Jean-Luc Pamart; Francois-Xavier Ollivier; Jerome Robillart
- Web page: https://patentgrep.com/patent/US8090268B2

## CPC

- H04J 3/0685: {Clock or time synchronisation in a node; Intranode synchronisation}
- H04J 14/02: Wavelength-division multiplex systems
- H04J 14/0298: {with sub-carrier multiplexing [SCM]}
- H04L 7/0041: {Delay of data signal}
- H04L 7/027: extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
- H04L 7/04: Speed or phase control by synchronisation signals {(H04L7/0075 takes precedence)}
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A process for transmitting data on an optical fiber including multiplexing in wavelength signals coming from a plurality of monochrome transmitters, each of which has its own wavelength, and modulating information to be transmitted by a carrier realized per channel, wherein timing (clocking) of each transmitter is controlled by a common clock.

## Claims

### Claim 1

A process for transmitting data on an optical fiber comprising:
wavelength division multiplexing of signals coming from a plurality of monochrome transmitters, each of which has its own wavelength and a slave local clock,
modulating information to be transmitted by a carrier realized per channel, and
reformatting a non-return to zero (NRZ) formatted, multiplexed signal to a return to zero (RZ) multiplexed signal or to carrier suppression return to zero (CS-RZ) multiplexed signal with an optical gate comprising an electro-optical modulator and a clock,
wherein said reformatting is common and simultaneous for all carriers in the multiplexed signal, and
wherein each slave local clock from each transmitter is controlled by a synchronization circuit comprising a master clock and a phase locked loop (PLL), said master clock controlling the clock of said optical gate and each slave local clock by using said phase locked loop which supplies the synchronization signal for each of the transmitters.

### Claim 2 (depends on 1)

The process according to claim 1, wherein the reformatting comprises optimizing the form of the signal as a function of characteristics of propagation of an associated transport means.

### Claim 3 (depends on 1)

The process according to claim 1, wherein the reformatting comprises optimizing optical parameters of the signal as a function of the characteristics of propagation of an associated transport means.

### Claim 4 (depends on 1)

The process according to claim 1, wherein the reformatting comprises an operation of stabilizing temporal parameters of data.

### Claim 5 (depends on 1)

The process according to claim 1, comprising synchronizing streams (pulses) emitted by the transmitters.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the reformatting comprises aligning the phase of signals generated by the transmitters.

### Claim 7 (depends on 6)

The process according to claim 6, wherein the aligning is subject to ambient parameters to compensate for temporal signal variations.

### Claim 8 (depends on 6)

The process according to claim 6, wherein the aligning is subject to ambient parameters to compensate for differences and variations between optical paths.

### Claim 9 (depends on 1)

The process according to claim 1, wherein each element of the multiplexer is signed before multiplexing by a frequency marker applied on the phase.

### Claim 10 (depends on 1)

The process according to claim 1, wherein each element of the multiplexer is signed before multiplexing by a frequency marker applied on the amplitude.

### Claim 11 (depends on 10)

The process according to claim 10, wherein the marker comprises a signal with a predetermined spectrum.

### Claim 12 (depends on 10)

The process according to claim 10, wherein the marker comprises a signal with a spectrum whose characteristics are a function of disturbances undergone by the signal on a corresponding path.

### Claim 13 (depends on 10)

The process according to claim 10, wherein characteristics of the marker are determined to disturb a marked signal in such a manner that marking is evanescent during passage through the gate.

### Claim 14

An apparatus for transmitting data on an optical fiber comprising a plurality of monochrome transmitters, each of which has its own transmission wavelength, with each transmitter having a local slave clock;
a multiplexer for wavelength division multiplexing signals coming from said plurality of monochrome transmitters;
an optical gate that comprises an electro-optical modulator and a clock and that receives multiplexed non-return to zero (NRZ) formatted signals and that reformats said multiplexed non-return to zero (NRZ) formatted signals to multiplexed return to zero (RZ) signals or to multiplexed carrier suppression return to zero (CS-RZ) signals, said reformatting being common and simultaneous for all carriers in the multiplexed signal; and
a synchronization circuit comprising a master clock controlling the clock of said optical gate and each slave local clock with a phase locked loop which supplies the synchronization signal for each of the transmitters.

### Claim 15 (depends on 14)

The apparatus according to claim 14, further comprising frequency marking circuits for each element of the multiplex.

### Claim 16 (depends on 15)

The apparatus according to claim 15, wherein each of the frequency marking circuits applies the marking signal onto one of the transmitters.

### Claim 17 (depends on 15)

The apparatus according to claim 15, wherein each of the frequency marking circuits applies the marking signal onto synchronizer of each path.

### Claim 18 (depends on 14)

The apparatus according to claim 14, wherein the optical gate comprises a detector for each marker to control characteristic of the formatting and adjustment of the phase of a corresponding path.

### Claim 19 (depends on 14)

The apparatus according to claim 14, wherein the optical gate comprises a spectral analyzer for the marker to adjust the phase of each path.

### Claim 20 (depends on 14)

The apparatus according to claim 14, further comprising an optical converter, a demultiplexer and a clock connected to at least one of the converters.

### Claim 21

A counter-reaction circuit for an apparatus that transmits data on an optical fiber comprising a plurality of monochrome transmitters, each of which has its own transmission wavelength, with each transmitter having a local slave clock; an optical gate that comprises an electro-optical modulator and a clock and that receives multiplexed non-return to zero (NRZ) formatted signals and that reformats said multiplexed non-return to zero (NRZ) formatted signals to multiplexed return to zero (RZ) signals or to multiplexed carrier suppression return to zero (CS-RZ) signals; and an automatic controller of each transmitter phase comprising a master clock and a phase locked loop (PLL), said master clock controlling the clock of said optical gate and each slave local clock by using said phase locked loop which supplies the synchronization signal for each of the transmitters, wherein said counter-reaction circuit generates a frequency marker for injecting a disturbing spectral signal of each transmitter and further comprises a detector of an output signal from the optical gate which acts on the automatic controller of each transmitter phase to produce a selected spectral transformation of each marker.