FR2879863A1 - Optical signal`s chromatic dispersion compensating device for e.g. field of optical telecommunication through optical guides, has switches to switch optical path of signal between two paths situated between inlet and outlet - Google Patents

Abstract

The device has an inlet (E) to receive an optical signal, and chromatic dispersion compensators (C1, C2) tunable in determined dispersion compensation ranges (G1, G2). Switches (COM1, COM2) with external switching access controls, switch optical path of the signal between two paths (V1, V2) situated between the inlet (E) and an outlet (S). The compensators (C1, C2) are placed in the paths.

Description

The invention relates to a dispersion compensation device

chromatic of an optical signal.

  One field of application of the invention is that of optical telecommunications by guides or optical fibers.

  One of the problems posed by the transmission of signals in optical guides is the chromatic dispersion of the optical signal transmitted by them with respect to the optical signal sent thereto.

  This phenomenon is due to the variations of the characteristics of the guide as a function of the wavelength of the optical signal.

  Thus, in an optical fiber, the index depends on the wavelength.

  The consequence of this phenomenon is that the group speed of the signal (or group delay, or group delay), which is by definition equal to the derivative of the phase of the signal with respect to its pulsation, depends on the frequency and is therefore not constant as a function of frequency.

  For a pulse signal, chromatic dispersion results in a temporal expansion of the pulses and a temporal overlap of successive pulses over long transmission distances, causing bit errors to the receiver. The chromatic dispersion is therefore even more serious than the signal bit rate is large, and is particularly penalizing from 10 Gbit / s.

  Many devices have been created to compensate for chromatic dispersion.

  Since the chromatic dispersion compensation required at the receiver to maintain optimal system performance can vary over time, dispersion compensators have to be provided, the dispersion compensation of which can be controlled. These dispersion compensators are said to be tunable and have a range of dispersion compensation, hereinafter referred to as the dispersion range. The dispersion compensation corresponds to the slope of the group delay curve as a function of the wavelength in the compensator, in picoseconds per nanometer. The dispersion compensator compensation range corresponds to the terminals between which the slope of the group delay vs. wavelength curve can be changed by external control. The dispersion compensation and the dispersion compensation range are generally valid in one or more wavelength ranges. The dispersion compensation range reflects the difference in compensation of the group delay per unit wavelength between the two ends of a wavelength range in which the compensator is active.

  These tunable dispersion compensators make it possible to correct the chromatic dispersion accumulated on a transmission line dynamically, for example in reconfigurable networks, in particular metropolitan networks, to take account of all the paths accessible to the optical signal in a node of routing, or to account for changes in environmental conditions (eg temperature, vibrations) disturbing the conditions of propagation of the optical signal in a slow variation of the effective fiber index.

  In the field of optical instrumentation, a chromatic dispersion compensator tunable over a wide range is also of great interest. Indeed, all components and subsystems of telecommunication equipment are tested in the laboratory under conditions close to reality. Currently, these tests are conducted with different sections of fiber to simulate this or that optical architecture. This solution is expensive, complex and cumbersome to implement. The phenomena related to the dispersion can be advantageously simulated with a tunable dispersion emulator device. As before, the more tuning range will be important, the more the component will be able to simulate architectures with long fiber lengths. The reproducibility of the dispersions, the compactness and the capacity of the device to generate positive and negative dispersions, are goals to be achieved in this field.

  The two main known techniques for producing tunable chromatic dispersion compensators are the Bragg grating and the Gires-Tournois interferometer (or standard cavity). Below are examples of embodiments of tunable chromatic dispersion compensators using one or the other of these techniques.

  In WO 2004/012365, the compensator comprises a circulator, having an input port receiving the incident optical signal, an input / output port for sending the incident signal to a Bragg grating and receiving the signal reflected by this one, and a signal output port. A dispersion tuning device accords the characteristic dispersion profile of the Bragg grating by applying a thermal gradient thereto. A dispersion controller takes a fraction of the output signal to control the dispersion tuning device. The dispersion range of this compensator is from -400 ps / nm to + 400 ps / nm.

  WO 03/087906 discloses a method for producing a tunable filter by applying a force, comprising a Bragg grating. Further described is a system for recovering the filtered signal at the output of a three port circulator, receiving on its input the signal and connected by its intermediate port to the filter. A feedback loop includes a measurement device responsive to the response of the filter and a module controlled by the measuring device to control the traction and temperature of the filter.

  In document US 2003/0086168, the tunable dispersion compensator comprises a beam splitter, for separating the incident beam into two sub-beams, which are sent to the two arms of a Michelson interferometer, connected to each other by a network of beams. Bragg.

  US 2003/0099019 discloses a dispersion compensation system, comprising cascaded standard stages, wherein the output port of each calibration stage is coupled by two circulators to the input port of the next calibration stage. Each standard stage has a front reflective coating and a rear reflective coating. In one of the standard stages, the point of incidence of the optical path on the front reflective coating is movable, thereby adjusting the reflectivity of the latter by adjusting the position of the point of incidence. The system is tunable to dispersion values ranging from -500 ps / nm to +500 ps / nm.

  In US 2002/0181106, standard units are cascaded to a multi-port circulator. Each standard unit has a first reflective surface receiving an incident signal and a second reflective surface, which process the signal according to a scatter function based on the incident position of the signal.

  The devices of the state of the art described above have the drawback of having a relatively narrow dispersion compensation range.

  Mention may also be made of configuration devices HOM (in English Hich Order Mode for high-order mode fibers) or VIPA (in English Virtual Image Phase Array for virtual image phase matrix).

  In HOM-configured devices, a higher order mode of a slightly multimode fiber may have a negative dispersion of up to -800 ps / (nm.km) if it is located near the cutoff. A chromatic dispersion compensator is made using mode converters on either side of a section of this fiber, but the compensator can be tunable only discontinuously.

  The VIPA optical systems compensate for a dispersion between -800 ps / nm and +800 ps / nm. They include a collimating lens, a cylindrical lens, a glass slide, and a focusing lens for focusing light onto a three-dimensional mirror. The different wavelengths are reflected in different places of the mirror. The value of the dispersion is tunable by moving the mirror.

  However, these two solutions are complex in structure and are even more expensive and cumbersome than the previous devices. In addition, they are less flexible than these.

  The object of the invention is to provide a device for compensating for the chromatic dispersion of an optical signal, overcoming the aforementioned drawbacks of the state of the art and making it possible to increase the range width over which compensation can be granted.

  For this purpose, the object of the invention is a device for compensating for the chromatic dispersion of an optical signal, comprising: an input intended to receive the optical signal; and at least one first chromatic dispersion compensator, tunable in a first range. defined dispersion compensation device, characterized in that it further comprises - at least one second chromatic dispersion compensator, which is tunable in a second determined dispersion compensation range, - switches of the optical path of the signal between at least a first path and a second path, which are located between the input and an output, the first compensator being respectively in the first and / or second path, and the second compensator being respectively in the second or first path.

  Thanks to the invention, at least one degree of freedom is available to select the dispersion compensation by the switches and achieve significant compensation ranges.

  The invention also relates to a device for compensating the chromatic dispersion of an optical signal, comprising - an input intended to receive the optical signal and - at least one first chromatic dispersion compensator, tunable in a first dispersion range determined and provided on the optical path of the signal between the input and an output, characterized in that it further comprises: - at least one second chromatic dispersion compensator, - at least one third chromatic dispersion compensator, and - switches of the optical path of the signal between at least a first path and a second path, the first path corresponding to the serialization of the first compensator and the third compensator, the second path corresponding to the serialization of the first compensator and the second compensator , and the second and third compensators being tunable in the second and third ranges respectively s of dispersion determined and disjoined from each other.

  The subject of the invention is also a device for compensating the chromatic dispersion of an optical signal, comprising: an input intended to receive the optical signal; and at least one first chromatic dispersion compensator, tunable in a first range of defined dispersion and located in a first channel included in the optical path of the signal between the input and an output, characterized in that it further comprises, in series with the first channel and between the input and the output, switches of the optical path of the signal between - at least one second path having at least one second chromatic dispersion compensator, which is tunable in a second range of determined dispersion compensation, and - at least one third dispersion path not included in the second dispersion range.

  According to other features of the invention, the third channel has a substantially zero chromatic dispersion; - the third channel is free of chromatic dispersion compensator; or the third channel comprises at least one third chromatic dispersion compensator, tunable in a third range of determined dispersion compensation, which is disjoint with respect to the second dispersion compensation range; According to one embodiment, the switches are able to switch in addition to an additional chromatic dispersion channel substantially zero and, in the latter case, the switches are for example each composed of two switches between two positions.

  According to another embodiment of the invention, between the input and the output and in series with the switches of the second channel and the third channel are provided switches of the first channel and a 1 o fourth channel of dispersion different from the dispersion compensation range of the first channel.

  The fourth channel has a substantially zero chromatic dispersion, or the fourth channel has at least a fourth chromatic dispersion compensator, tunable in a fourth range of determined dispersion compensation, which is disjoint with respect to the first dispersion range.

  In another embodiment, the chromatic dispersion compensation device comprises at least: a switch of the input on either the first channel comprising the first compensator, or on the fourth channel comprising the fourth compensator, a switch connected to the first and fourth channels, allowing switching from either the first channel to a first intermediate output, or from the fourth channel to the first intermediate output, or from the first channel to a second intermediate output, or from the fourth channel to the second output intermediate, a switch connected to the second intermediate output to switch it either on the third channel containing the third compensator, or on the second channel containing the second compensator, a switch connected to a third intermediate output to switch to the third intermediate exit is the third way, so it the second channel, a switch connected to the output and switching either the first intermediate output or the third intermediate output on this output. According to other features of the invention, the overall chromatic dispersion compensation ranges associated with the paths form a chromatic dispersion compensation range, continuous between a lower bound and an upper bound; the compensators comprise a Bragg grating, or a standard cavity; at least one pair of compensators comprises a common Bragg grating, attacked by opposite ends on each compensator of the pair; at least one pair of compensators located between the switches has opposite dispersion compensation ranges; the compensators have dispersion compensation ranges of the same width; the switches each comprise at least one switching control access from the outside; - Switch control accesses are software controlled; at least one optical amplifier is provided between the input and the output; - The optical amplifier is adjustable gain.

  The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example with reference to the accompanying drawings, in which: FIG. 1 schematically represents a first embodiment of the compensation device According to the invention, FIG. 2 schematically represents the first embodiment comprising a single Bragg grating; FIG. 3 schematically represents a second embodiment of the chromatic dispersion compensation device according to the invention, FIG. 4 schematically represents a comparative example of a chromatic dispersion compensation device according to the invention; FIG. 5 is a schematic representation of a third embodiment of the chromatic dispersion compensation device according to the invention; FIG. a fourth embodiment of the com device According to the invention, FIG. 7 schematically represents a fifth embodiment of the chromatic dispersion compensation device according to the invention. FIG. 8 schematically represents a sixth embodiment of the dispersion compensation device. 9 schematically represents a seventh embodiment of the chromatic dispersion compensation device according to the invention; FIG. 10 schematically represents an eighth embodiment of the chromatic dispersion compensation device according to the invention; FIG. 11 shows the different possible signal paths in the eighth embodiment of FIG. 10, and the dispersion ranges associated with these paths; FIG. 12 schematically represents a ninth embodiment of the device of FIG. chromatic dispersion compensation According to the invention, FIG. 13 schematically illustrates the transmission curve and three signal group delay curves for -300 ps / nm, 0 ps / nm and + 3000 ps / nm chords of the ninth embodiment. FIG. 14 diagrammatically represents the transmission curve and three signal group delay curves for -400 ps / nm, 0 ps / nm and + 400 ps / nm chords of the comparative example of FIG. FIG. 4 for two cascaded elemental compensators, and FIG. 15 schematically shows the transmission curve 1 o and three signal delay curves for agreements of -400 ps / nm, -600 ps / nm and -800 ps. / nm of the comparative example of Figure 4 for a single elementary compensator.

  In the embodiments shown in the figures, the compensation device according to the invention comprises an input E intended to be connected to an optical fiber carrying an optical signal, an output S and chromatic dispersion compensation means between the input E and the output S. In the following, the chromatic dispersion compensation means comprise individual chromatic dispersion compensators, able to compensate for the group delay of the signal sent on their input port, with a compensation value which can be selected or tuned from the outside in a given dispersion compensation range, as shown by the oblique arrows in the figures, means for controlling the dispersion compensating value being provided for this purpose on the compensator. These individual chromatic dispersion compensators may be of any known type and may be of different types from one another.

  In the figures, by way of illustrative example, each chromatic dispersion compensator is produced by a so-called elementary compensator, consisting mainly of a CD dispersive component and a CIR multi-port circulator, of which an input PE port and a PS output port respectively form the input port and the output port of the compensator, and an intermediate port PI is connected to the elementary dispersive component CD, able to compensate for the chromatic dispersion of the signal sent to it by this port intermediate PI, the compensation value granted in the compensation range. This elementary dispersive component CD operates for example in reflection, to return to the intermediate port PI the corrected signal of the compensation value granted on this component. This elementary dispersive component is, for example, a variable pitch Bragg grating. It could also be a Gires-Tournois interferometer. The circulator could be replaced by any other means of 1 o coupling. The elementary dispersive component has, for example, a range of continuous compensation between a lower bound, typically a few hundred ps / nm, and an upper bound typically ranging up to 1500 to 2000 ps / nm. Typically and currently, the upper bound of the compensation range has the same sign as its lower bound, without understanding the zero of dispersion. The different compensators may have opposite ranges and / or the same width, for example when they are between the same switches between the channels where they are.

  According to the invention, the device comprises a number n greater than or equal to 2 of possible paths for the optical path of the signal, going from the input E to the output S, and switches that can be controlled from the outside for pass the optical path of the signal through one of these channels. The switches are controlled from the outside each on their control access for example by appropriate software for controlling their operation.

FIRST EMBODIMENT

  In the embodiment shown in FIG. 1 are provided, among these n channels, two channels V1, V2, with in the path V1 a dispersion compensator C1 and in the other path V2 another dispersion compensator C2. A switch COM1 from the input E to the selected one of the first and second channels VI, V2 (of the type 2879863 12 switch 1 to 2), and a switch COM2 of the selected channel from the two channels V1, V2 to the second one. output S (switch type 2 to 1) are provided, the selection of the channel V1 or V2 connected between the input E and the output S being operated by an external switching control access AC1, AC2, respectively provided on the switches COM1 and COM2. Thus, when the channel VI is selected on the switches COM1 and COM2, the signal passes through the first optical path going from the input E, to the switch COM1, to the channel V1, to the switch COM2 and to the output S and, when the channel V2 is selected on the switches COM1 and COM2, the signal passes through the second optical path going from the input E, to the switch COM1, to the channel V2, to the switch COM2 and to the output S. The channels are oriented from generally in the direction from input E to output S and, in the case of channels having one or more compensators, in the direction from the input port to the output port of the compensators. In Figure 1, the paths of the optical path, which can be provided in addition to VI and V2 and may also include a compensator, are not shown.

  The compensators C1, C2 respectively have G1 and G2 ranges of dispersion compensation, different from each other. These ranges G1 and G2 may have common parts or, as will be supposed to be the case below, be disjoined.

  The channel VI, the compensator C1 and the range G1 play the role of the first channel V1, first compensator C1 and first range G1, while the channel V2, the compensator C2 and the range G2 act as the second channel V2, second compensator C2 and second range G2.

  For example, the G1 range of Cl ranges from -1500 ps / nm to 750 ps / nm and the C2 range of G2 ranges from +750 ps / nm to +1500 ps / nm. Thus, the overall compensation range of the device of FIG. 1 has a width of 1500 ps / nm.

  As is shown in FIG. 2 and in a general manner for the embodiments of the invention, the compensators C1 and C2 located between the same switches COM1, COM2 can be made by elementary compensators having as their component elemental dispersive CD a common Bragg grating, attacked by opposite ends E1, E2. The Bragg grating CD is connected by a first end E1 to the intermediate port P1 of the circulator CIR1 of the compensator C1, and by its second end E2, remote from the first end E1, to the intermediate port P12 of the circulator CIR2 of the compensator C2. Thus, the network CD compensates for the dispersion of a value + VD in the channel V1 and the opposite value VD in the channel V2, and in this case the ranges G1 and G2 are of opposite values.

SECOND EMBODIMENT

  In the embodiment shown in FIG. 3, the compensation device is based on the one described above with reference to FIG. 1, and further comprises, in series with the assembly formed by the switches COM1, COM2 and the channels VI, V2 can be switched therebetween, a path V3 for passing the optical signal between the input E and the output S. This channel V3 is therefore situated between the input E and the switch COM1, as this is represented in FIG. 3, or between the switch COM2 and the output S. In the channel V3 is a dispersion compensator C3, tunable in a dispersion compensation range G3.

  Channel VI, compensator C1 and range G1 play the role of third channel V1, third compensator C1 and third range G1. The V2 channel, the C2 compensator and the G2 range play the role of second channel V2, second C2 compensator and second G2 range. The V3 channel, the compensator C3 and the G3 range play the role of first channel V3, first compensator C3 and first range G3.

  The first optical path thus passes through the first channel V3 and the third channel V1 when the channel V1 is selected on the switches COM1 and COM2, while the second optical path passes through the first channel V3 and the second channel V2. channel V2 is selected on the switches COM1 and COM2.

  Thus, if G1 = [a, b], G2 = [c, d] and G3 = [e, f], where b> a, d> c, f> e, the overall compensation range of the device will be G = [a + e, b + f] U [c + e, d + f], having an overall width of (b + fae) + (d + f- ce), for the first and second optical paths, respectively.

  The sum of the individual widths of the ranges G1, G2, G3 of the individual compensators being (ba) + (dc) + (fe), the device will have a gain 1 o GL in range of dispersion compensation, defined by the overall width optical paths on the sum of the individual widths, equal to GL = 1 + (fe) / (b-a + d-c + fe) which will therefore be greater than one.

  Thus, there will be a larger dispersion compensation width gain than in the case of a simple serialization of two or three compensators C1, C'2, C'3, represented in FIG. has a gain in width GL equal to one. Thus, in the numerical example where a = e = + 750 ps / nm, b = f = + 1500 ps / nm, c = -1500 ps / nm and d = -750 ps / nm, GL = 1.33 at Figure 3, against 1 in Figure 4.

  In each embodiment, the gain GL corresponds to the actual gain in dispersion compensation width, when the global ranges of the different optical paths are disjoint, or have only one upper or lower bound in common.

  The ranges G1, G2, G3 are for example such that the overall range of the first path passing through the channel V3 and the channel VI, is continuous with the overall range passing through the channel V3 and the channel V2, that is to say say that the overall range of the first path has an upper or lower bound, or a portion, that is common with the overall range of the second path, for the global ranges to cover a single full interval. To do this, in the previous case, the ranges G1, G2, G3 must respect the condition c + e <_ b + f and d> b, so that the overall range of V3, V2 follows the global range of ( V3, V1), or conversely a + e <_d + f and c <a, so that the global range of (V3, V1) follows the global range of (V3, V2). For c + e = b + f and d> b, the global range of the second path begins where the global range of the first path stops, and conversely for a + e = d + f and c <a, the global range from the first path starts there, stops the overall range of the second path. In these two cases, the real gain in dispersion compensation width corresponds to the gain GL.

  Furthermore, in general, a path having an overall range of dispersion compensation containing the dispersion zero can be obtained, and can be centered on the dispersion zero, for example by providing at least one positive compensation range. and at least one negative compensation range for the individual compensators traversed by this path.

THIRD EMBODIMENT

  In the embodiment shown in FIG. 5, based on that described above with reference to FIG. 3, the compensator C1 is omitted and replaced by a simple transmission line LT in the channel VI between the switches COM1 and COM2. Thus the channel V1 located between the switches COM1 and COM2 has zero dispersion compensation, and the overall range of dispersion compensation from the input E to the output S is equal to the range G3 of the compensator C3 for the first path passing through V3 and V1. In this case, in the above, a = b = 0, and the gain GL in dispersion compensation range width is equal to GL = 1 + (fe) / (d-c + fe), ie GL = 1.5 in the previous numerical example.

  The condition of continuity will therefore be verified for c + e sf and d> 0, so that the overall range of the second path passing through the channel V3 and the channel V2 follows the overall range of the first path passing through the channel V3 and the channel V1. , or conversely e <_ d + f and c <0, so that the overall range of the first path passing through the V3 channel and the V1 channel follows the overall range of the second path passing through the V3 channel and the V2 channel.

FOURTH EMBODIMENT

  In the embodiment shown in FIG. 6, an additional channel LT with zero dispersion compensation, analogous to the channel LT described above, is added between the switches COM1 and COM2 with respect to the embodiment of FIG. 3, to be able to be switched by them in a third optical path, thus passing through the V3 channel and this path LT (the switch COM1 being in this case a switch 1 to 3 and the switch COM2 being a switch 3 to 1). The overall signal compensation range of this third optical path is therefore equal to G3.

  The GL gain in dispersion compensation width range is then equal to GL = 1+ 2 (f-e) / (b-a + d-c + f-e) and will therefore be larger than in the previous embodiments. Thus in the numerical example above, GL = 1.66.

  The conditions of continuity of the global ranges of compensations of the first, second and third paths borrowing respectively the channel V1, V2 and LT selected are deduced from those of the two previous embodiments, the role of the channels VI and V2, and therefore ranges G1 and G2 can be permuted therein.

FIFTH EMBODIMENT

  In the embodiment shown in FIG. 7, equivalent to that represented in FIG. 6, the switch COM1 is replaced by a first switch COM11 of the channel V3 on the one hand to the channel LT and on the other hand to the input E12 of a second switch COM12, 3o ensuring the switching between the channels V1 and V2. Conversely, the switch COM2 is replaced by a third switch COM21 switching channels' V1 and V2 on its output S21, and a fourth switch COM22, switching the channel LT and the output S21 to the output S These switches COM11, COM12, COM21, COM22 respectively have an external switching control access AC11, AC12, AC21, AC22, the switches COM11 and COM12 being in this case each a switch 1 to 2, and the switches COM21 and COM22. each being a 2-to-1 switch.

SIXTH EMBODIMENT

  In the embodiment shown in FIG. 8, taking again that of FIG. 3, the switches COM1 and COM2 of the channels V1 and V2 are put in series with other switches COM3 and COM4 of the same type making it possible to select either the channel V3. , the fourth channel V4 between these switches COM3 and COM4. Thus, four optical paths are provided between the input E and the output S: the first path passing through the path VI and the path V3, the second path passing through the path V2 and the path V3, the third path passing through the path V1 and V4 channel, the fourth path through V2 and V4 channel. In FIG. 8, the fourth channel V4 contains a fourth dispersion compensation compensator C4, of range G4, for example equal to [g, h], different from the range G3. The GL gain in range of dispersion compensation compensation is then equal to 2, higher than that of the previous embodiments. The overall compensation range of the four paths can be set continuously by a corresponding choice of compensator ranges.

SEVENTH EMBODIMENT

  In the embodiment shown in FIG. 9, taking again that of FIG. 8, the fourth compensator C4 is replaced by the zero dispersion line LT described above in the channel V4, also having a gain GL = 2.

EIGHTH EMBODIMENT

  In the embodiment represented in FIG. 10, taking again that of FIG. 8, the device comprises: the switch COM3 of the input E, making it possible to switch either on the channel V3 comprising the compensator C3, or on the V4 channel 5 comprising the compensator C4, a switch COM5 (switch type 2 to 2) for performing one of the following switches: V3 channel to an output S51 (first intermediate output S51), the V4 channel to the output S51, channel V3 to another output S52, channel V4 to output S52 (second intermediate output S52), - switch COM1 connected to output S52 to switch this output S52 to channel V1 containing compensator C1 either on the channel V2 containing the compensator C2, the switch COM2 connected to the output S21 (third intermediate output S21) to switch to this output S21 is the channel V1 containing the compensator C1, or the channel V2 containing the compensator C2,a switch COM6 connected to the output S and switching either the output S51 or the output S21 on this output S (switch from type 2 to 1).

  The switches COM3, COM5, COM1, COM2, COM6 are able to be controlled by external control access ports AC3, AC5, AC1, AC2, AC6, to pass the signal through one of the following six paths of the input E at the exit S: the first path 1 passing through the track V3 and the track VI, the second path 2 passing through the track V3 and the track V2, the third path 3 passing through the track V4 and the track V1, the fourth path 4 via V4 and V2, the fifth path 5 through V3 and S51, the sixth path 6 through V4 and S51 output.

  The gain GL in dispersion compensation range is equal to GL = 2 + (f-e + hg) (f-e + h-g + b-a + dc) and is therefore greater than that of previous realization.

  In the numerical example where a = e = + 750 ps / nm, b = f = + 1500 ps / nm, c = g = -1500 ps / nm and d = h = -750 ps / nm, GL = 2.5.

  This case is illustrated in FIG. 11, representing the different global ranges of the paths 1, 2, 3, 4, 5, 6. The actual overall compensation range of the device will in this case be continuous from -3000 ps / nm to + 3000 ps / nm, and represents a real gain in dispersion compensation width, with respect to the sum of the widths of the individual ranges of compensators C1, C2, C3, C4, equal to 6000/3000 = 2. This real gain is less than GL gain because we can notice that paths 3 and 4 have the same 1 o overall range of -750 ps / nm to +750 ps / nm.

Ninth Embodiment

  In the embodiment shown in FIG. 12, similar to that of FIG. 10, the compensators C1 and C2 are made by elementary compensators having, as elementary dispersive component CD1, a common Bragg grating, attacked by opposite ends E1, E2. , respectively connected to the intermediate port P11, P12 of their circulator CIRI, CIR2, and the compensators C3 and C4 are made by elementary compensators having as elementary dispersive component CD2 another common Bragg grating, attacked by opposite ends E3, E4, connected respectively to the intermediate port P13, P14 of their circulator CIR3, CIR4. The G1 range is therefore of opposite sign to the G2 range, and the G3 range is of opposite sign to the G4 range. This results in a double real gain in dispersion compensation width using only two dispersive elements each having a compensation width of 750 ps / nm in the above example.

  The transmission R and the group delay TPG of the device according to the eighth embodiment are shown in FIG. 13. The curve of the group delay as a function of the wavelength is given for three different dispersion agreements of the compensators in FIG. overall range at -3000 ps / nm, 0 ps / nm and +3000 ps / nm, these scatter chords corresponding to the slope of the curves. By varying the adjustment value of the compensation of the different compensators in their individual ranges G1, G2, G3, G4, the slope of the curves is thus varied between -3000 ps / nm and +3000 ps / nm, ie substantially more than in FIG. 14 for the two cascaded elemental compensators of FIG. 4, having a dispersion compensation range of -400 ps / nm and + 400 ps / nm, and more than in FIG. single elemental compensator of Figure 4, having a dispersion compensation range of -800 ps / nm to -400ps / nm.

  In general, an optical amplifier may be provided between the input E and the output S to amplify the signal before it is sent to this output S, to compensate for the losses of the device. This amplifier is for example adjustable gain to compensate for the variation of the losses occurring when the dispersion compensation of the compensators is granted.

2879863 21

Claims (20)

  1. A device for compensating the chromatic dispersion of an optical signal, comprising - an input (E) intended to receive the optical signal and - at least one first chromatic dispersion compensator (C1, C3) tunable in a first range ( G1, G3), characterized in that it further comprises - at least one second chromatic dispersion compensator (C2), which is tunable in a second range (G2) of determined dispersion compensation, switches (COM1, COM2) of the optical path of the signal between at least a first path and a second path, which are located between the input (E) and an output (S), the first compensator (C1, C3) being respectively in the first and / or second path, and the second compensator (C2) being respectively in the second or first path (V2, VI).   Chromatic dispersion compensation device according to Claim 1, characterized in that the first chromatic dispersion compensator (C3) is provided in a first channel (V3) situated in series with the switches (COM1, COM2) on the first and second optical paths of the signal between the input (E) and the output (S), the first optical path corresponding to the serialization of the first channel (V3) and a third channel (V1) of dispersion not included in the second dispersion compensation range (G2), the second optical path corresponding to the series connection of the first channel (V3) and a second channel (V2), in which is located the second compensator (C2) of chromatic dispersion, the switches (COM1, COM2) being able to ensure switching at least between the second channel (V2) and the third channel (V1).   2879863 22 3. chromatic dispersion compensation device according to claim 2, characterized in that the third channel (VI) has a substantially zero chromatic dispersion.   4. Chromatic dispersion compensating device according to claim 2 or 3, characterized in that the third channel (V1) is free of chromatic dispersion compensator.   5. Chromatic dispersion compensation device according to claim 2, characterized in that the third channel (VI) comprises at least one third chromatic dispersion compensator (C1), 1 o tunable in a third range (C1) compensation of determined dispersion, which is disjoint with respect to the second dispersion compensating range (G2).   6. chromatic dispersion compensation device according to claim 5, characterized in that the switches (COM1, COM2) are able to switch in addition to an additional channel (LT) chromatic dispersion substantially zero.   Chromatic dispersion compensation device according to Claim 6, characterized in that the switches (COM1, COM2) are each composed of two switches (COM1, COM12, COM21, COM22) between two positions.   Chromatic dispersion compensation device according to Claim 5, characterized in that between the input (E) and the output (S) and in series with the switches (COM1, COM2) of the second channel (V2). and of the third channel (V1) there are provided switches (COM3, COM4) of the first channel (V3) and a fourth channel (V4) of dispersion different from the range (G3) of dispersion compensation of the first channel. (V3).   9. Chromatic dispersion compensation device according to claim 8, characterized in that the fourth channel (V4) has a substantially zero chromatic dispersion.   10. Chromatic dispersion compensation device according to claim 8, characterized in that the fourth channel (V4) comprises at least one fourth chromatic dispersion compensator (C4), tunable in a fourth range (G4) for compensation of the chromatic dispersion. determined dispersion, which is disjunct with respect to the first dispersion range (G3).   11. Chromatic dispersion compensation device according to claim 10, characterized in that it comprises at least: a switch (COM3) of the input (E) on either the first channel (V3) comprising the first compensator (C3), or on the fourth channel (V4) comprising the fourth compensator (C4), - a switch (COM5) connected to the first and fourth channels (V3, 1 o V4), allowing the switching of the first channel (V3) ) to a first intermediate output (S51), either from the fourth channel (V4) to the first intermediate output (S51), or from the first channel (V3) to a second intermediate output (S52), or from the fourth channel ( V4) to the second intermediate output (S52), - a switch (COM1) connected to the second intermediate output (S52) for switching it to the third channel (VI) containing the third compensator (C1), or on the second channel (V2) containing the second compensator (C2), - u n switch (COM2) connected to a third intermediate output 20 (S21) for switching to this third intermediate output (S21) is the third channel (V1) or the second channel (V2), - a switch (COM6) connected to the output (S) and switching either the first intermediate output (S51) or the third intermediate output (S21) to this output (S).   Chromatic dispersion compensation device according to one of the preceding claims, characterized in that the overall chromatic dispersion compensation ranges associated with the paths form a continuous chromatic dispersion compensation range between a lower terminal and a terminal. higher.   13. Chromatic dispersion compensation device according to any one of the preceding claims, characterized in that the compensators comprise a Bragg grating, or a standard cavity.   2879863 24 Chromatic dispersion compensating device according to one of the preceding claims, characterized in that at least one pair of compensators (C3, C4; C1, C2) comprises a common Bragg grating attacked by ends ( E1, E2) opposite each compensator (C3, C4; C1, C2) of the pair.   15. Chromatic dispersion compensation device according to any one of the preceding claims, characterized in that at least one pair of compensators (C3, C4, C1, C2) located between the switches (COM3, COM5, COM1, COM2 ) has opposing dispersion compensation ranges.   Chromatic dispersion compensating device according to one of the preceding claims, characterized in that the compensators (C3, C4; C1, C2) have dispersion compensation ranges of the same width.   Chromatic dispersion compensation device according to one of the preceding claims, characterized in that the switches each comprise at least one switching control access from the outside.   Chromatic dispersion compensation device according to claim 17, characterized in that the switching control ports are software controlled.   Chromatic dispersion compensation device according to one of the preceding claims, characterized in that at least one optical amplifier is provided between the input (E) and the output (S).   20. Chromatic dispersion compensation device according to any one of the preceding claims, characterized in that the optical amplifier is adjustable gain.