Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0685—Clock or time synchronisation in a node; Intranode synchronisation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0298—Wavelength-division multiplex systems with sub-carrier multiplexing [SCM]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
  • H04L7/0033—Correction by delay
  • H04L7/0041—Delay of data signal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
  • H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/04—Speed or phase control by synchronisation signals

Definitions

• the present invention relates to the field of signal transmissions on a line between a transmitter and a receiver.
• the present invention relates more particularly to the long distance transmission of the signal over a link comprising a succession of several sections of optical fiber of approximately 100 kilometers.
• the first techniques used to solve this problem were to install signal regeneration stations.
• the signal is first converted to an electronic signal, regenerated, and retransmitted.
• this regeneration system was very expensive.
• Another known solution is that of optical amplification.
• the chromatic dispersion of the wavelength is compensated by an opposite dispersion fiber, and the attenuation is compensated by an optical amplifier.
• This solution requires high performance transmitters and receivers and remains expensive in single channel.
• multi-channel solutions were quickly necessary.
• a plurality of transmitters use separate wavelengths.
• the data is then modulated with quasi-monochromatic signals and the amount of information transmitted is therefore increased.
• the signals are then multiplexed before transmission over the optical line. Amplification and optical compensation are then carried out simultaneously on the multiplex. This method has the disadvantage of using very expensive transmitters for each channel.
• the present invention intends to remedy the drawbacks of the prior art by proposing a method of pooling performance for long distance optical transmission.
• the present invention is of the type described above and it is remarkable, in its broadest sense, in that it provides a method for the transmission of data over an optical fiber comprising a step of length multiplexing d wave of signals from a plurality of monochrome transmitters each having its own wavelength and a step of modulation by the information to be transmitted from a carrier produced per channel, characterized in that the timing of each of said transmitters is controlled by a common clock.
• the method further comprises a step of shaping common and simultaneous to all the carriers.
• the shaping step consists in optimizing the shape of the signal as a function of the propagation characteristics of the associated means of transport.
• the shaping step consists in optimizing the optical parameters of the signal as a function of the propagation characteristics of the associated means of transport.
• the shaping step includes an operation for stabilizing the time parameters of the data stream.
• the method further comprises a step of synchronizing the 'trains emitted by said monochrome emitters.
• the shaping step comprises an operation of aligning the phase of the signals generated by said transmitters.
• the alignment operation is slaved to ambient parameters in order to compensate for temporal variations of signals.
• the alignment operation is subject to ambient parameters in order to compensate for the differences and variations between the optical channels.
• each element of the multiplex is signed before the multiplexing step by a frequency marker applied to the phase.
• each element of the multiplex is signed by a frequency marker applied to the amplitude.
• said marker consists of a signal having a predetermined spectrum.
• said marker is constituted by a signal having a spectrum whose characteristics are a function of the disturbances undergone by the signal on the corresponding channel.
• the characteristics of the marker are determined to disturb the signal marked in such a way that the marking is evanescent when passing through the door.
• the present invention also relates to equipment for the transmission of data over an optical fiber, comprising a plurality of monochrome transmitters each having its own emission wavelength, and a multiplexer characterized in that it comprises a clock master controlling the slave clocks of each of said transmitters.
• the equipment further comprises an optical gate receiving the multiplex of optical carriers, as well as a cutting signal produced by said master clock.
• it also includes. frequency marking circuits for each element of the multiplex.
• each of said frequency marking circuits applies the marking signal to one of the transmitters.
• each of said frequency marking circuits applies the marking signal to the synchronization means of each channel.
• the optical door includes means for detecting each marker to control the characteristics of shaping and adjusting the phase of the corresponding channel.
• the optical gate comprises means of spectral analysis of the marker for adjusting the phase of each channel.
• the present invention also relates to equipment for the regeneration of data on an optical fiber of the opto-electronic conversion means, a demultiplexer, and a clock connected to at least one of said converters.
• the present invention further relates to a feedback circuit for data transmission equipment on an optical fiber characterized in that it generates a frequency marker for injecting a disturbing spectral signal from a transmitter, and comprises a means for detecting the output signal of a gate to act on a means for controlling the phase of the transmitter to obtain the desired spectral transformation of each marker.
• FIG. 1 represents a diagram of transmission over an optical line by a wavelength comb according to the prior art
• FIG. 2 represents a diagram of transmission over an optical line by a wavelength comb according to the invention
• FIG. 3 represents the block diagram of an equipment for the transmission of data over an optical fiber according to the invention
• FIG. 4 represents the case of a regeneration site according to the invention.
• FIG. 5 represents the formation of an RZ type signal from the associated NRZ signal.
• the n TX transponders transmit according to distinct wavelengths.
• the signals are multiplexed by the multiplexer M and then transmitted over the long distance optical line (L).
• the n transponders must be of high performance to allow transmission.
• the synchronization equipment associated with the feedback loop makes it possible to obtain a pooling of the performance of the transponders.
• the signal quality is thus obtained after passing through the synchronization equipment according to the invention, which makes it possible to use transponders of lower quality and therefore of low cost.
• the equipment comprises the following functional sub-assemblies:
• a transmission part comprising a plurality of transponders (4) allowing the synchronization of the flows incoming on the local rhythm from the synchronization block (2)
• a multiplexer (5) receiving as input the signals from each of the transponders and delivering a multiplex signal
• An optical door (1) ensuring the shaping of the multiplex signal
• a synchronization circuit (2) controlling the clock of the optical door as well as the local clocks (11) of each of the transponders
• a signal processing circuit (3) delivering disturbance signals acting on the phase of the clocks of the transponders.
• the transmission part implements N monochrome transponders.
• Each transponder delivers a colored optical signal, having a specific wavelength.
• the carrier of each transponder is modulated by the information to be transmitted in a known manner.
• Each transponder has a local clock (11). This local clock is a slave clock controlled by the master clock (6) of the synchronization circuit (2).
• the equipment can also optionally include a means for generating a data stream to be transmitted. Such a means obtains data and an associated frequency supplied by a clock of period equal, depending on the application, to that of a binary data element.
• the transponder according to the invention also comprises means for modulating an optical source by a signal from a data generator.
• the signal is also amplified in order to be adapted electrically to the components.
• the amplifiers may be of low cost.
• the light source whose amplitude is to be modulated may possibly, in the case of a WDM system, require the use of a wavelength control device.
• the pre-emphasis of the level of each of the optical tributaries of the door can be achieved by means of a fixed or adjustable optical amplification device for example of SOA technology (Semiconductor Optical Amplifier), EDFA (Erbium Dopped Fiber Amplifier) , or fiber.
• Amplification at the optical door output allowing the optical level at the line input to be adapted can be carried out by the same means as mentioned above.
• the electro-optical modulation device can be either a direct modulation of the source laser, or else a modulation of the source light by means of an electro-optical modulator of the LiN03 or electro-absorption type.
• the two types of modulator have the advantage of being low cost.
• the synchronization block (2) can either be autonomous with its own oscillator, or connected to an external reference.
• the clock resulting from the choice of one of these two sources serves as a low frequency driver for the high frequency PLL which provides the cutout signal at the door.
• the phase locked loop (PLL) of the synchronization block (2) also provides the synchronization signal for each of the transmitters (4). It also performs the phase adjustment of each of the channels to compensate for the aging of the optical fiber, the demultiplexer and the transmitter.
• the function of the signal processing block (3) is to create marked disturbers for each transmission channel. It also allows a spectral analysis of the markers after transformation through the optical gate (1). This analysis is done by fast Fourier transform (FFT) and by digital filtering. It also controls the transmitters using the PID (Proportional, Integral, Derivative) method, which adjusts the measured points to a set of set points.
• FFT fast Fourier transform
• PID Proportional, Integral, Derivative
• the disturbers are applied to the delay elements of the synchronization block ( ⁇ i, ⁇ 2 , -, ⁇ n ). These disturbers are specific modifications of the phase or the amplitude of the signals as a function of the transmission channel, these disturbances being applied at the level of the delay lines and not at the level of the transponders, the operation is done at low speed. , thereby reducing implementation costs.
• These are, according to a preferred embodiment, signals having a determined spectrum, one for each channel to be marked. This spectrum can also depend on the characteristics of the disturbances undergone by the signal on each channel. Furthermore, after passing through the optical door, this marking by disturbers must not modify the information. These are therefore filtered at the optical door.
• the information transmitted from the Digital Signal Processor DSP or signal processing unit (8) to the delay lines ( ⁇ i, ⁇ 2 , ..., ⁇ n ) include the phase control resulting from the PID and the various disturbers from n separate digital / analog converters (7).
• the data is received by the DSP after optoelectronic conversion by a converter (10) and digitization by an analog / digital converter (9).
• the signal processing block (3) also allows an analysis of the marked signals in order to adjust the phases of each channel. This analysis is a spectral analysis of the specific markers and a detection of these markers in the main signal.
• the optical door (1) comprises an electrooptical modulator, for example of the Mach-Zehnder type.
• the optical flux coming from the transponder modulated by the data to be transmitted is of the NRZ (Non Return to Zero) type.
• NRZ coding is a type of binary coding where, for example, 0 is represented by a voltage of 0 Volts and 1 by V Volts.
• the NRZ format is very sensitive to optical noise and non-linearities, as opposed to symmetrical RZ (Return to Zero) coding, where the 0 is coded by 0 V and the 1 by a transition from V volts to 0 Volts.
• RZ coding is particularly suitable for long distance transmissions. This type of coding is also less costly in equipment.
• the optical door (1) converts the coding from NRZ to RZ allowing robust transmission.
• the use of a modulator allowing a phase inversion of the optical signal as is the case for the Mach-Zehnder, also authorizes the implementation of the CS-RZ (Carrier Suppression RZ) format.
• This format obtained by the application on the optical gate with a frequency half that applied in the case of RZ modulation, has the advantages of spectral width of the NRZ format and the advantages of the noise robustness of the R format.
• Figure 5 shows the different representations of the data for transmission.
• the signal RZ is obtained by cutting the sequence NRZ at least from a clock of period identical to that of the binary element of the stream to be modulated, using the external modulator.
• the optical gate (1) also optimizes the optical parameters of the received signal, in particular in the form of a reduction in the chirp of the signal.
• the optical gate (1) performs an operation of stabilizing the temporal parameters of the data flow, in particular in the form of a reduction in the jitter of the modulating signal.
• 3R regeneration involves reshaping the pulses in the amplitude domain (2R regeneration for Re- amplification and Re-shaping) and in the time domain (Re-timing).
• a demultiplexer makes it possible to separate the signals to be regenerated (after a drop in level or a chromatic dispersion).
• the signals pass through optoelectronic (O / E) converters.
• O / E optoelectronic
• the opto-electronic converters are then connected to the n transponders and to the equipment described in FIG. 3, comprising the optical door (1), the synchronization block (2) and the signal processing block (3).
• delays introduced by this regeneration mode are of the electrical type following the opto-electronic conversion.

Applications Claiming Priority (5)

Publications (1)

Family

ID=32511525

Family Applications (1)

Country Status (6)

Families Citing this family (20)

Family Cites Families (14)

• 2003
  • 2003-10-15 CA CA002508296A patent/CA2508296A1/fr not_active Abandoned
  • 2003-10-15 US US10/536,954 patent/US8090268B2/en active Active
  • 2003-10-15 WO PCT/FR2003/050094 patent/WO2004054151A1/fr not_active Application Discontinuation
  • 2003-10-15 AU AU2003288377A patent/AU2003288377A1/en not_active Abandoned
  • 2003-10-15 EP EP03780293A patent/EP1568166A1/de not_active Withdrawn
  • 2003-10-15 BR BR0316942-1A patent/BR0316942A/pt not_active IP Right Cessation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events