Optical communication

Abstract

Examples are provided showing a method for determining data from one or more optical communications, a computer program product, a non-transient recording medium, and a data processing device enabling the implementation of the method. Figure from the abstract: [Fig. 8]

Description

Title of the invention: Optical communication technical field

[0001] This disclosure relates to the field of optical communications. Previous technique

[0002] Optical communications, that is to say communications using light as a data transmission vector, are widely used.

[0003] In particular, in optical fibers, a transmitter emits a laser guided by the optical fiber towards a receiver. Generally, the transmitter also has a receiver function, just as the receiver also has a transmitter function. This is then referred to as a transceiver or a transmitter / receiver.

[0004] Optical communications use complex techniques and technologies which can sometimes pose certain difficulties.

[0005] The present disclosure improves this situation. Summary

[0006] In this regard, a method for determining data from one or more optical communications is proposed, the method comprising: obtaining a sampled electrical signal from an electrical signal generated by the reception of an optical signal transmitted by an optical transmitter in a first optical channel, the optical transmitter and the first optical channel forming a first transmission set; determine a filter to apply to the sampled electrical signal in order to equalize a frequency response of the first transmission set; determine a Fourier transform of the filter; determine an inverse of the Fourier transform of the filter; and determine a bandwidth of the first transmission set from the inverse of the Fourier transform of the filter. This process makes it possible to determine the bandwidth of a transmission system comprising an optical transmitter and an optical channel without invasive operation on the optical transmitter.

[0007] Optionally, the first optical channel has a length less than a first threshold, the first threshold being chosen to be able to neglect the effect of the first optical channel on the bandwidth of the first transmission set. This option makes it possible, in particular, to determine the bandwidth of the optical transmitter of the transmission set.

[0008] Optionally, the method is implemented a second time using a second optical channel with a length greater than a second threshold, the optical emitter and the second optical channel forming a second transmission set. Thus, the second implementation of the method makes it possible to determine a bandwidth for the second transmission set. The second threshold can be chosen to allow consideration of the effect of the second optical channel on the bandwidth of the second transmission set. In this option, the method may further include determining the bandwidth of the second optical channel from the difference between the bandwidth of the second transmission set and the bandwidth of the first transmission set. This option makes it possible to estimate the bandwidth of the second optical channel of the second transmission set.

[0009] Optionally, the bandwidth of the second optical channel may include a chromatic dispersion parameter of the second optical channel and a frequency shift parameter of a laser in the optical emitter. In this option, the method may further include determining at least one of the chromatic dispersion parameter and the frequency shift parameter of the laser from the bandwidth of the second optical channel.

[0010] Optionally, the chromatic dispersion parameter of the second optical channel is predetermined; and the determination of at least one of the chromatic dispersion parameter and the frequency shift parameter of the laser may include the determination of the frequency shift parameter of the laser from the bandwidth of the second optical channel and from the predetermined chromatic dispersion parameter.

[0011] Optionally, the laser frequency shift parameter is predetermined; and the determination of at least one of the chromatic dispersion parameter and the laser frequency shift parameter may include the determination of the chromatic dispersion parameter of the second optical channel from the bandwidth of the second optical channel and from the predetermined frequency shift parameter.

[0012] Optionally, the determination of at least one of the chromatic dispersion parameter and the frequency shift parameter of the laser may include the determination of the chromatic dispersion and the frequency shift parameter of the laser from a fitting method matching the frequency shift and chromatic dispersion parameters of a representative function of a bandwidth of a theoretical optical channel, with the determined bandwidth of the second optical channel.

[0013] Optionally, the optical signal corresponds to a determined electrical signal converted by the optical emitter; the sampled electrical signal comprises a plurality of samples; and determining a filter to be applied to the sampled electrical signal in order to equalize the frequency response of a transmission set may include: determining a filter comprising a plurality of coefficients; where each coefficient of the filter can be associated with a respective sample of the plurality of samples of the sampled electrical signal, and where the values ​​of the filter coefficients are determined from an optimization method allowing to minimize an error between the determined electrical signal and the electrical signal filtered by the filter.

[0014] Optionally, determining a filter to be applied to the sampled electrical signal in order to equalize the frequency response of a transmission set may further include: selecting a sub-part of the filter comprising a specific parameter having an associated value in a time impulse response of the filter that is the highest among the respective values ​​of the filter parameters in that impulse response; the selected sub-part of the filter corresponding to the filter to be applied to the sampled electrical signal in order to equalize the frequency response of the transmission set.

[0015] The application also relates to a data processing device comprising a processing circuit for the implementation of any of the processes presented in this disclosure.

[0016] The application further relates to a computer program product comprising instructions for implementing any of the processes presented in this disclosure when that program is executed by a processor.

[0017] Finally, the application relates to a non-transient computer-readable recording medium on which is recorded a program for the implementation of any of the processes presented in this disclosure when that program is executed by a processor. Brief description of the drawings

[0018] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0019] [Fig.1] schematically represents an example of a system according to the present disclosure.

[0020] [Fig.2] schematically represents another example of a system according to the present disclosure.

[0021] [Fig.3] schematically represents yet another example of a system according to the present disclosure.

[0022] [Fig.4] schematically represents an example of an optical emitter.

[0023] [Fig.5] schematically represents an example of an optical receiver.

[0024] [Fig.6] schematically represents an example of an optical transceptor.

[0025] [Fig.7] schematically represents an example of a processing device data.

[0026] [Fig.8] schematically represents an example of a method for determining data from one or more optical communications.

[0027] [Fig.9] schematically represents another example of a method for determining data from one or more optical communications.

[0028] [Fig. 10] schematically represents yet another example of a method for determining data from one or more optical communications.

[0029] [Fig. 11] schematically represents several particular examples of implementation of a specific operation of the example of data determination process illustrated in [Fig. 10].

[0030] [Fig. 12] schematically represents a particular example of the implementation of a specific operation of an example of a data determination process.

[0031] [Fig. 13] schematically represents another specific example of the implementation of a specific operation of an example of a data determination process. Description of embodiments

[0032] Since optical communications are complex to implement, manufacturers who offer optical transceptors enabling the implementation of these communications generally offer fully integrated optical transceptors.

[0033] The inventor noted that the fact that optical transceptors offered by manufacturers are fully integrated poses a problem when these transceptors are evaluated in the laboratory by a network operator, particularly when testing the transceptors before deploying them on the optical communication network. Indeed, it is not easily or economically feasible to disassemble several specific components of a transceptor in order to evaluate each component individually and determine its characteristics of interest. Furthermore, even if it were easy to disassemble specific components of a transceptor, this operation could damage them, and if the transceptor were to be reused, it would have to be reassembled in any case, which, in addition to being time-consuming, requires additional expertise.

[0034] It is thus understood that the evaluation of a large volume of optical transceptors is not compatible with disassembly and reassembly operations of each of the transceptors.

[0035] Furthermore, when evaluating a transceiver without disassembling it, one is forced to provide the transceiver with an input test signal that must correspond to the input signal format it processes to function. In other words, an input signal for testing the transceiver cannot be an electrical signal specifically chosen for the evaluation, but must be a signal that allows the transceiver to function normally.

[0036] This disclosure also proposes a solution for estimating the bandwidth of a transmitter in an optical communication system, which in some examples corresponds to the bandwidth of an optical transceiver, without disassembling the transceiver. The proposed solution cleverly uses a filter to equalize the frequency response of the transmitting part of the optical communication in order to determine, from the inverse of the Fourier transform of this filter, the bandwidth of this transmitting part. The filter can, for example, be a parametric filter whose coefficients are modified by an optimization method that minimizes the error between the reconstructed electrical signal and the originally transmitted electrical signal.

[0037] Indeed, since the filter equalizes the transmission channel, this means that the reconstructed signal corresponds to the electrical signal supplied to the transmitting part of the transceiver for transmission. Therefore, it is clear that the filter's bandwidth compensates extremely well, even perfectly, for the bandwidth of the transmitting part of the transceiver. This means that the bandwidth of the transmitting part of the transceiver is the inverse of the equalizing filter's bandwidth. By determining the inverse of the Fourier transform of this filter, the bandwidth of the transmitting part of the transceiver can thus be precisely determined without disassembling any component of the transceiver.

[0038] The proposed solution therefore makes it possible to characterize precisely the bandwidth of the emitting part of an optical transceptor in a non-invasive manner for this transceptor, so that this solution can be repeated easily and quickly for each optical emitter (or optical transceptor as appropriate) to be evaluated.

[0039] It is now presented with reference to figures 1 to 3 of the examples of systems 10 in which the examples of method 100 for determining data from one or more optical communications can be implemented, which will be presented later in the document.

[0040] The system 10 includes an optical emitter 2. The optical emitter 2 is configured to convert electrical signals into optical signals. More specifically, The optical transmitter 2 is configured to convert an incoming electrical signal into an optical signal and transmit this optical signal over an optical channel C to an optical receiver 3. The optical transmitter 2 can also be an optical transceiver 4 (capable of both transmitting and receiving). The optical signal transmitted by the optical transmitter 2 in the optical channel C is therefore a specific electrical signal converted by the optical transmitter 2. In one option, the electrical signal to be transmitted can be predetermined and then sent to the optical transmitter 2 for transmission in the optical channel C. In another option, the electrical signal to be transmitted can be converted into an optical signal without knowing its content and then determined subsequently from the electrical signal generated by the optical receiver 3.

[0041] An example of an optical transmitter 2 is shown in particular in [Fig. 4]. The optical transmitter 2 may, for example, comprise a clock data recovery module 23, a laser control module 22, and an optical transmission module 21, which includes the laser (for example, a laser diode). Thus, when an electrical signal to be transmitted is presented as an input to the optical transmitter 2, the clock of this signal is extracted by the clock data recovery module 23, the laser control module 22 determines the parameters (in particular intensity, shape, and duration) of the laser pulses, and the optical transmission module 21 emits the corresponding pulses into the optical channel C via the laser.

[0042] The system 10 also includes an optical receiver 3. The optical receiver 3 is configured to convert optical signals into electrical signals. More precisely, the optical receiver 3 is configured to convert an optical signal it receives from an optical channel into an electrical signal and optionally transmit this electrical signal. The optical receiver 3 can, in particular, correspond to an optical transceiver 4 (capable of both transmitting and receiving).

[0043] An example of an optical receiver 3 is shown in particular in [Fig. 5]. The optical receiver 3 may, for example, comprise a receiver chain including an optical receiver module 31 (designated as "Receiver Optical Sub-Assembly"), a transimpedance amplifier 32, a limiter 33, and a clock recovery module 34. Thus, when an optical signal from an optical channel C is received by the optical receiver 3, the optical receiver module 31 converts this optical signal into an electrical signal (for example, using a photodiode), the transimpedance amplifier 32 amplifies the converted electrical signal, the limiter 33 limits the signal to a predetermined voltage range to protect the system, and the clock recovery module 34 recovers the clock from this signal. The value of the data can be determined by thresholding. The signal amplitude is limited. Specifically, in some examples, the data value can be 0 when the signal is below a predetermined threshold or 1 when the signal is above that threshold. These examples use direct pulse amplitude modulation (2-PAM) with a single comparison threshold, but other amplitude modulations with multiple threshold levels to encode a plurality of bits can be used (e.g., 4-PAM).

[0044] An example of an optical transceiver 4 is shown in [Fig. 6]. This example includes the optical transmitter 2 shown in [Fig. 4] and the optical receiver 3 shown in [Fig. 5]. In addition to the optical transmitter 2 and optical receiver 3 examples, the optical transceiver 4 also includes a diplexer 41. The diplexer 41 allows the same optical channel C to be used for both transmitting and receiving optical signals. In particular, the diplexer 41 minimizes interference between the signals transmitted and received on the optical channel C.

[0045] Thus, it is understood that in the example of system 10, both the optical emitter 2 and the optical receiver 3 can each correspond to an optical transceiver 4.

[0046] The system 10 comprises an optical channel C, that is, an optical transmission channel separating the optical emitter 2 from the optical receiver 3. The optical channel C can be defined as a medium that allows optical signals to pass between the optical emitter 2 and the optical receiver 3. The optical channel C can, for example, allow light signals to be directed from the optical emitter 2 to the optical receiver 3 within a limited volume. The optical transmission channel C can, for example, correspond to an optical fiber.

[0047] The optical emitter 2 and the optical channel C form a transmission system whose bandwidth B will be determined by the method examples 100 presented below. The bandwidth B of a transmission system can be defined as a frequency range in which the attenuation of the signal transmitted by the transmission system is less than an attenuation threshold. The attenuation threshold can, for example, be equal to 3 decibels (dB). Indeed, the optical emitter 2 has a bandwidth that will affect the electrical signal it transmits, and will notably distort it. Furthermore, the optical channel C, when it has a sufficiently large length L, can also have a bandwidth that will affect the transmitted optical signal, and will therefore distort the transmitted optical signal.

[0048] In initial examples schematically represented in [Fig. 2], the optical channel C corresponds to a first optical channel CL. The first optical channel Cl has a length L less than a first threshold SL. The optical emitter 2 and the first optical channel Cl thus form a first transmission set. The first threshold S1 is determined so that the effect of the first optical channel Cl on a bandwidth B1 of the first transmission set can be neglected. Neglecting the effect of an optical channel on the bandwidth of a transmission set can mean that the attenuation of a signal passing through that transmission set due to the optical channel is less than a predetermined attenuation threshold over a specific frequency range. Those skilled in the art know that the bandwidth of a signal transmitted through an optical channel is affected in a non-negligible way only when the optical channel, for example, the optical fiber, has a sufficient length L. Therefore, the length L of the first optical channel Cl is chosen so that the effects of this first optical channel Cl on the bandwidth B1 of the first transmission set can be neglected.The first threshold SI can, for example, be defined as less than 100 meters, less than 50 meters, less than 30 meters, less than 10 meters, or even less than 1 meter. In particular, in these first examples, the optical receiver 3 can be directly connected to the optical emitter 2 so that the first optical channel Cl formed between the laser of the optical emitter 2 and the optical receiving module 31 of the optical receiver 3 can be on the order of a few centimeters.

[0049] In the second examples schematically represented in Figure 3, the optical channel C corresponds to a second optical channel C2. The second optical channel C2 has a length L greater than a second threshold S2. The optical emitter 2 and the second optical channel C2 thus form a second transmission set. The second threshold S2 is determined to allow consideration of the effect of the second optical channel C2 on a bandwidth B2 of the second transmission set. Considering the effect of an optical channel on a bandwidth of a transmission set may mean that the attenuation of a signal passing through this transmission set due to the optical channel is greater than the attenuation threshold determined over the specific frequency range determined.As explained previously, those skilled in the art know that the bandwidth of a signal transmitted through an optical channel is affected in a non-negligible way only when the optical channel, for example, the optical fiber, has a sufficient length L. Therefore, the length L of the second optical channel C2 is chosen to consider the effect of this second optical channel C2 on the bandwidth of the second transmission set. The second threshold S2 can, for example, be determined to be greater than 100 meters, greater than 110 meters, greater than 200 meters, greater than 500 meters, or even greater than 1 kilometer. These second examples will be used to determine, from the bandwidth B1 of the first transmission set and from the bandwidth B2 of the second transmission set, the bandwidth B3 of the second transmission channel C2. Indeed, . Since the second transmission channel C2 affects the bandwidth B2 of the second transmission set, the bandwidth B2 of the second transmission set includes portions induced by both the optical emitter 2 and the second transmission channel C2, which cannot be distinguished. However, knowing the bandwidth B1 of the first transmission set (which actually corresponds to the bandwidth of the optical emitter 2, since the effects of the first optical channel C1 on this bandwidth B1 are negligible), we can distinguish, within the bandwidth B2, the portion of this bandwidth that corresponds to the bandwidth B3 associated with the second optical channel C2. This bandwidth B3, however, includes a frequency shift df of the laser (referred to as the "laser chirp") of the optical emitter 2, as will be explained later.The laser's frequency shift df is sometimes referred to as "laser chirp" in the literature. Specifically, the laser's frequency shift df may include at least one of either a transient frequency shift α of the laser (referred to as "transient chirp") or an adiabatic frequency shift °e of the laser (referred to as "adiabatic chirp"). These transient frequency shifts α and adiabatic frequency shifts °c of the laser are phenomena known to those skilled in the art.

[0050] The system 10 also includes a sampler 5 for sampling the electrical signal generated by the reception of an optical signal at the optical receiver 3.

[0051] The system 10 finally includes a data processing device 6 configured for the implementation of any one of the example methods 100 described in this disclosure. An example of a data processing device 6 is shown schematically in [Fig. 7].

[0052] The data processing device 6 may include a PROC calculation circuit and a MEM memory.

[0053] A PROC computing circuit may, for example, comprise at least one of the following: a processor, a microprocessor, a controller, a microcontroller, or an FPGA. The PROC computing circuit is particularly well-suited for performing Fourier transforms. The PROC computing circuit may, for example, implement a computational step using complex numbers.

[0054] The MEM memory may, for example, comprise at least one of the following: ROM (Read-Only Memory), RAM (Random Access Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or any other suitable type of storage medium. The MEM memory may, for example, comprise optical, electronic, or magnetic storage media.

[0055] The MEM memory can, for example, store code instructions which, when executed by the PROC computing circuit, cause the data processing device 6 to implement any of the example processes 100 presented in this disclosure.

[0056] In a first option, the data processing device 6 may also include a wired or wireless communication interface INT connected to a corresponding communication interface of the sampler 5. In this way, the sampled electrical signal can be communicated to the data processing device 6 for processing at a location distant from the sampler 5. In a second option, the sampler 5 may be integrated into the data processing device 6. In this second option, samples of the electrical signal generated by the reception of an optical signal at the optical receiver 3 may, for example, be stored in the MEM memory. Furthermore, in this second option, the data processing device 6 may, for example, be an oscilloscope.

[0057] An example of a method 100 for determining data from one or more optical communications is now presented with reference to [Fig. 8]. This example of a method 100 can, for example, be implemented by the data processing device 6.

[0058] It should be noted that the figures associated with the process examples 100 are merely illustrations of the process examples 100, representing, by means of blocks, the various operations that may be included in the process and described later in this document. As such, the illustrations do not convey any sequence between the operations. In other words, the operations described with reference to the figures are not necessarily carried out sequentially and may, in particular, be carried out in a different order than that shown in the figures, or be carried out in parallel, unless a given operation requires a result from another operation to be carried out. Similarly, it is not necessary for each operation to be carried out once before the same operation is repeated a second time.The frequency with which each operation is implemented is specific to it and is not necessarily linked to the implementation of other operations.

[0059] As illustrated by block 110, the method 100 includes an operation for obtaining a sampled electrical signal x[k]. The sampled electrical signal x[k] can be obtained from an electrical signal generated by the reception of an optical signal transmitted by the optical emitter 2 in the first optical channel CL. As explained previously, the optical emitter 2 and the first optical channel Cl form the first transmission set.

[0060] The electrical signal generated by the reception of an optical signal transmitted by the optical transmitter 2 can correspond to the electrical signal generated by the optical receiver 3 upon receiving the optical signal. This electrical signal generated by the optical receiver 3 can then be sampled by the sampler 5 to obtain the sampled electrical signal x[k]. The sampled electrical signal x[k] can thus comprise a plurality of samples, each representative of a level of the analog electrical signal generated by the optical receiver module 31 at a respective time instant.

[0061] As illustrated by block 120, the method 100 includes an operation for determining a filter h[k] to be applied to the sampled electrical signal x[k]. The filter h[k] is applied so as to equalize a frequency response of the first transmission set. In examples, applying the filter h[k] to the sampled electrical signal x[k] so as to equalize a frequency response of the first transmission set can be equivalent to applying the filter h[k] to the sampled electrical signal x[k] such that the difference between the electrical signal to be transmitted by the optical emitter 2 and the sampled electrical signal x[k] is less than a predetermined difference threshold.

[0062] The frequency response of a transmission set can refer to the intrinsic ability of the transmission set to distort the amplitude and phase of the electrical signal to be transmitted by the optical transmitter 2, as a function of the frequency of this signal, before being received by the optical receiver 3.

[0063] In examples, the operation 120 of determining the filter h[k] can be carried out from an optimization method.

[0064] As illustrated by block 130, the method 100 includes an operation to determine a Fourier transform h[f] of the filter h[k]. Performing a Fourier transform h[f] of the filter h[k] allows us to obtain the bandwidth of the filter h[k].

[0065] As illustrated by block 140, the process 100 includes an operation to determine an inverse of the Fourier transform h[f] of the filter h[k]. This is indeed the inverse of the Fourier transform h[f], that is, -L. It is not a the inverse Fourier transform.

[0066] Finally, as illustrated by block 150, the method 100 includes an operation of determining the bandwidth B1 of the first transmission set from the inverse -L of the Fourier transform h[f] of the filter h[k].

[0067] Insofar as the h[k] filter makes it possible to equalize the frequency response of the first transmission set, this means that the signal reconstructed at the output of the filter corresponds to the electrical signal supplied to the optical transmitter 2 for its transmission. Therefore, the bandwidth of the filter h[k] compensates excellently, or even perfectly, for the bandwidth of the first transmission set. Consequently, the bandwidth of the first transmission set corresponds approximately to the inverse of the bandwidth of the filter h[k] used for equalization. By determining the inverse of the Fourier transform of this filter h[k], we can thus precisely determine the bandwidth of the first transmission set. Since the first transmission set includes the optical emitter 2 and the first optical channel Cl, whose length has been determined to neglect the effects of the optical channel on the bandwidth, method 100 therefore allows us to determine the bandwidth of an optical emitter 2.

[0068] Thus, method 100 makes it possible to estimate the bandwidth of an optical emitter 2 (which may constitute the transmitting part of an optical transceiver) without disassembling any element of the optical emitter 2 (or the transceiver, as the case may be). As such, determining the bandwidth of the optical emitter 2 does not require expertise in disassembling / reassembling a specific optical emitter. It can be performed in the same way on different types of optical emitters without needing specific expertise in the components of each type of optical emitter. Furthermore, method 100 can be implemented on a large volume of emitters to test them before integrating them into the network much more easily than through the use of disassembly / reassembly operations.

[0069] Other operations may optionally be incorporated into Process 100 and are described later in this disclosure. These operations may be incorporated into Process 100 in combination with each other unless expressly stated otherwise in this disclosure.

[0070] In examples, the method 100 can be implemented a second time using the second optical channel C2 having a length L greater than the second threshold S2. As explained previously, the optical emitter 2 and the second optical channel C2 therefore form the second transmission set.

[0071] Thus, in this second iteration of the method 100, the sampled electrical signal obtained during operation 110 is obtained from an electrical signal generated by the reception of an optical signal transmitted by the optical transmitter 2 in the second optical channel C2. The following operations 120, 130, 140, and 150 are implemented in the same way so that this second iteration of the method 100 makes it possible to determine the bandwidth B2 of the second transmission set.

[0072] It is therefore understood that in these examples, there are two optical communications. A first one through the first optical channel Cl in order to determine the band bandwidth Bl, and a second one through the second optical channel C2 in order to determine the bandwidth B2.

[0073] In examples in which the method is implemented again by obtaining the sampled signal from an optical transmission in the second optical channel C2, the method 100 may further include an operation 210 of determining a bandwidth B3 of the second optical channel C2 from a difference between the bandwidth B2 of the second transmission set and the bandwidth B1 of the first transmission set. These examples are schematically illustrated in [Fig. 9].

[0074] As explained previously, by knowing the bandwidth B1 of the first transmission set (which actually corresponds to the bandwidth of the optical transmitter 2 since the effects of the first optical channel C1 on this bandwidth B1 are negligible), we can distinguish, within the bandwidth B2, the portion of this bandwidth that corresponds to the bandwidth B3 associated with the second optical channel C2. These examples therefore allow us to characterize the bandwidth of the second optical channel C2.

[0075] In examples where the method 100 includes the operation 210 of determining the bandwidth B3 associated with the second optical channel C2, this bandwidth B3 includes a chromatic dispersion parameter D of the second optical channel C2, and a frequency shift parameter df of the laser of the optical emitter 2. The frequency shift parameter df of the laser may include at least one of the transient frequency shift α of the laser or the adiabatic frequency shift °c of the laser. Although the bandwidth B3 associated with the second optical channel C2 can be determined by reducing the effects related to the bandwidth of the optical emitter C3, this bandwidth B3 always includes a component related to the optical emitter 2 which corresponds to the frequency shift df of the laser of the optical emitter 2.The process 100 can thus include an operation 220 of determining at least one of the chromatic dispersion parameter D and the frequency shift parameter df of the laser from the bandwidth B3 associated with the second optical channel C2. These examples are illustrated schematically in [Fig. 10].

[0076] In initial examples in which the method 100 includes operation 220, the chromatic dispersion parameter D of the second optical channel C2 may be determined beforehand. For example, it may be determined beforehand on a test bench using methods known to those skilled in the art, or it may be supplied by the manufacturer of the second optical channel C2. In which case, operation 220, which determines at least one of the chromatic dispersion parameter D and the frequency shift parameter df of the laser, may include an operation of Determination of the laser frequency shift parameter df from the bandwidth B3 of the second optical channel C2 and from the predetermined chromatic dispersion parameter D. This operation is illustrated in [Fig. 1 1] by block 221a.

[0077] In second examples in which the method 100 includes operation 220, the frequency shift parameter df of the laser of the optical emitter 2 can be determined beforehand. It can, for example, be determined beforehand on a test bench using methods known to those skilled in the art, or it can be supplied by the manufacturer of the optical emitter 2. In which case, operation 220, which determines at least one of the chromatic dispersion parameter D and the frequency shift parameter df of the laser, may include an operation to determine the chromatic dispersion parameter D from the bandwidth B3 of the second optical channel C2 and from the predetermined frequency shift parameter df of the laser. This operation is illustrated in [Fig. 11] by block 221b.

[0078] In third examples in which the process 100 includes operation 220, operation 220 for determining at least one of the chromatic dispersion parameter D and the frequency shift parameter df of the laser may include an operation for determining the chromatic dispersion D and the frequency shift parameter df of the laser. This operation is illustrated in [Fig. 11] by block 221c.

[0079] In examples where the method 100 includes operation 221c, this operation 221c of determining the chromatic dispersion parameter D and the frequency shift parameter df of the laser can be performed using a fitting method. The fitting method can thus match the frequency shift parameter df (which may include the transient frequency shift α and / or the adiabatic frequency shift °c) of the laser and the chromatic dispersion parameter D of the second optical channel, belonging to a representative function of a bandwidth of a theoretical optical channel, with the determined bandwidth B3 of the second optical channel.

[0080] In particular, an example of a function representing a bandwidth of the theoretical optical channel may correspond to the following function:

[0081] I ( LDl^o \ . ( LDl^o \ \ washed H(O ) which corresponds to the H(o) — ।cos( 4pic / - sin\ 4pjc t- ° / 1 bandwidth of the theoretical optical channel as a function of the modulation frequency 0 applied to the optical signal; 0 which corresponds to the modulation frequency applied to the optical signal; L which corresponds to the theoretical optical channel length; O which corresponds to the chromatic dispersion of the theoretical optical channel; / 0 which corresponds to the wavelength of the optical signal; PI which corresponds to the number pi; c which corresponds to the speed of the optical signal; a which corresponds to the transient frequency shift of the laser; and °c which corresponds to the adiabatic frequency shift of the laser.

[0082] This function is notably presented in equations 2.16 and 2.28 of the document: Anet Neto, L. (2012). Study of the potential of multicarrier modulation techniques for future WDM and TDM PON optical access networks. Doctoral dissertation, High Frequency Electronics and Optoelectronics, University of Limoges, Faculty of Science and Technology, XLIM Laboratory, Department C2 S2: Components, Circuits, Signals and High Frequency Systems and Orange Labs, ASHA Unit: Advanced Studies on Home and Access Networks. Thesis No. 58-2012. With this function, the fitting method can thus determine the chromatic dispersion parameters D, the transient frequency shift α of the laser, and the adiabatic frequency shift °c of the laser.

[0083] Thus, in these examples, the adjustment method adjusts the parameters df (for example a and / or °c) and D to the bandwidth B3 of the second optical channel determined during operation 210 to identify them using this representative function.

[0084] This is of course only one example of a representative function and other examples of such a function could be considered in order to determine these parameters.

[0085] In examples, the operation 120 of determining the filter h[k] to be applied to the sampled electrical signal x[k] in order to equalize the frequency response of a transmission set may include an operation of determining a filter F comprising a plurality of coefficients. This operation is illustrated by block 121 in [Fig. 12]. Each coefficient of the filter F can be associated with a respective sample from the plurality of samples of the sampled electrical signal x[k]. In these examples, the values ​​of the coefficients of the filter F are determined using an optimization method that minimizes an error between the electrical signal to be transmitted by the optical transmitter 2 and the electrical signal filtered by the filter F. The aim is therefore to minimize the error between the original electrical signal to be transmitted by the optical transmitter 2 and the reconstructed signal at the output of the filter F after reception of the optical signal by the optical receiver 3..

[0086] In examples, the optimization method may, for instance, correspond to a Wiener filter. The Wiener filter minimizes the mean squared error between the samples of the desired signal (the original electrical signal to be transmitted) and the samples of the received signal (i.e., the samples of the sampled electrical signal x[k]). In other examples, the optimization method might be a least squares method. The least squares method minimizes the sum of the squared differences between samples of the desired signal (the original electrical signal to be transmitted) and samples of the received signal (the samples of the sampled electrical signal x[k]).

[0087] The Wiener filter is particularly advantageous for method 100 since it very effectively minimizes the error when using a large number of coefficients (and therefore a large number of samples). Thus, in examples, the sampled signal x[k] may, for instance, comprise more than 100 or even more than 1000 samples. However, method 100 can be implemented in the laboratory or on a test bench (i.e., not necessarily in real time), so the delay in the transmission of the filtered signal (induced by the use of filter F on the sampled electrical signal x[k]), which depends directly on the number of samples involved in calculating the coefficients of filter F, is not problematic from an application standpoint.Thus, determining a filter F that equalizes the frequency response of a transmission set using a Wiener filter yields a filter that very effectively compensates for the bandwidth B of the transmission set. Therefore, inverting this filter provides a fairly accurate representation of the bandwidth B of this transmission set.

[0088] In examples where method 100 includes operation 121, method 100 may further include an additional operation of selecting a sub-part Fi of the filter F comprising a specific coefficient from among the plurality of coefficients in the time impulse response of the filter F. The time impulse response of the filter F is to be understood as the impulse response, in the time domain, of the filter F. The specific coefficient may correspond to the coefficient having the highest value, in the time impulse response of the filter F, among the respective values ​​of the coefficients of the filter F in this impulse response. The value associated with a coefficient of the filter in its time impulse response reflects, in particular, the energy associated with this coefficient in the time domain. This operation is illustrated in [Fig. 13] by block 122.

[0089] The selection operation 122 of the sub-part Fi of the filter F may, for example, include multiplying the filter F determined at the end of operation 121 by a gate function in the time domain. Multiplying the filter F by a gate function in the time domain also means performing a convolution between the filter F and a cardinal sine function in the frequency domain. The center The gate function can, for example, be determined from the specific coefficient. In some examples, the gate function can be centered on the specific coefficient. In others, the gate function can have a defined width to retain only a specific number of coefficients from the filter F, including the specific coefficient.

[0090] In examples in which the method 100 includes the operation 122 of selecting the sub-part Fi of the filter F, the selected sub-part Fi may correspond to the filter h[k] to be applied to the sampled electrical signal in order to equalize the frequency response of the transmission set during the operation 120.

[0091] In this instance, the inventor noted that the filter F determined during operation 121 using the optimization method could be too sensitive, such that the bandwidth of this filter (obtained via its Fourier transform), although effectively compensating for the bandwidth of the transmission system, could be improved. The inventor astutely observed that by selecting a sub-part Fi of the filter F comprising the filter's specific coefficient associated with the highest value (and therefore the highest energy), this sub-part Fi compensated for the bandwidth of the transmission system better than the filter F. To this extent, the inverse Fourier transform of this sub-part Fi of the filter F (corresponding in these examples to the h[k] filter) better reflects the bandwidth of the transmission system than the filter F.Therefore, the bandwidth determined during operation 150 for the transmission set is more accurate using this sub-part Fi than using the entire filter F determined by the optimization method during operation 121.

[0092] This disclosure also presents a computer program product including instructions for implementing any of the processes described when this program is executed by a processor.

[0093] Furthermore, the application relates to a non-transient computer-readable recording medium on which is recorded a program for the implementation of any of the methods 100 presented in this disclosure when this program is executed by a processor.

[0094] Thus, the solution presented in this disclosure makes it possible to determine the bandwidth of a transmission system comprising an optical emitter (which may be integrated into an optical transceiver) and an optical channel without invasive operation on the optical emitter. In some examples, the solution makes it possible to determine both the bandwidth of the optical emitter and the bandwidth of the optical channel, again without performing any invasive operation on either of these elements. Furthermore, Other examples in this disclosure allow for the estimation of a chromatic dispersion parameter of the optical channel and a frequency shift parameter of the optical emitter laser from the bandwidth of the optical channel.

[0095] Since the solution does not require knowledge of the internal architecture of the optical transmitter, it can be implemented on different models of optical transmitters (for example, from different brands) without requiring specific expertise for each model. Furthermore, the solution can be implemented on a large volume of optical transmitters for testing before integrating them into the network without risk of degradation, and this is simplified compared to a process based on disassembling and reassembling these transmitters.

Claims

1. Demands Method (100) for determining data from one or more optical communications, the method comprising: obtaining (110) an electrical signal sampled from an electrical signal generated by the reception of an optical signal transmitted by an optical transmitter in a first optical channel (Cl), the optical transmitter and the first optical channel (Cl) forming a first transmission set; determine (120) a filter (h[k]) to be applied to the sampled electrical signal in order to equalize a frequency response of the first transmission set; determine (130) a Fourier transform of the filter (h[k]); determine (140) an inverse of the Fourier transform of the filter (h[k]); and determine (150) a bandwidth (Bl) of the first transmission set from the inverse of the Fourier transform of the filter (h[k]), in which the first optical channel has a length less than a first threshold (SI), the first threshold (SI) being chosen so as to be able to neglect an effect of the first optical channel on the bandwidth (B1) of the first transmission set, in which the method is implemented a second time using a second optical channel (C2) having a length greater than a second threshold (S2), the optical emitter and the second optical channel forming a second transmission set such that the second implementation of the method makes it possible to determine a bandwidth (B2) of the second transmission set; in which the second threshold is chosen to be able to consider an effect of the second optical channel on the bandwidth of the second transmission set; and in which the process further comprises: determine (210) a bandwidth (B3) of the second optical channel (C2) from a difference between the bandwidth of the second transmission set and the bandwidth of the first transmission set.

2. A method according to claim 1, wherein the bandwidth (B3) of the second optical channel (C2) comprises a chromatic dispersion parameter (D) of the second optical channel, and a frequency shift parameter (df) of a laser of the optical emitter; and wherein the method further comprises a determination (220) of at least one of the chromatic dispersion parameter (D) and the frequency shift parameter (df) of the laser from the bandwidth (B3) of the second optical channel (C2).

3. A method according to the preceding claim, wherein the chromatic dispersion parameter (D) of the second optical channel is predetermined; and the determination of at least one of the chromatic dispersion parameter and the frequency shift parameter of the laser comprises the determination (221a) of the frequency shift parameter (df) of the laser from the bandwidth (B3) of the second optical channel and from the predetermined chromatic dispersion parameter (D).

4. A method according to claim 2, wherein the frequency shift parameter (df) of the laser is predetermined; and the determination of at least one of the chromatic dispersion parameter (D) and the frequency shift parameter of the laser (df) comprises the determination (221b) of the chromatic dispersion parameter (D) of the second optical channel from the bandwidth (B3) of the second optical channel and from the predetermined frequency shift parameter (df).

5. A method according to claim 2, wherein the determination of at least one of the chromatic dispersion parameter (D) and the frequency shift parameter (df) of the laser comprises the determination (221c) of the chromatic dispersion (D) and the frequency shift parameter (df) of the laser from a fitting method matching the frequency shift parameters (df) and chromatic dispersion (D) of a representative function of a bandwidth of a theoretical optical channel, with the determined bandwidth of the second optical channel (B3).

6. A method according to any one of the preceding claims, wherein the optical signal corresponds to a determined electrical signal converted by the optical emitter (2); wherein the sampled electrical signal (x[k]) comprises a plurality of samples; wherein determining (120) a filter (h[k]) to be applied to the sampled electrical signal (x[k]) in order to equalize the frequency response of a transmission set comprises: determining (121) a filter (F) comprising a plurality of coefficients; wherein each coefficient of the filter (F) is associated with a respective sample of the plurality of samples of the sampled electrical signal, and wherein the values ​​of the coefficients of the filter (F) are determined from an optimization method for minimizing an error between the determined electrical signal and the electrical signal filtered by the filter.

7. A method according to the preceding claim, wherein determining (120) a filter (h[k]) to be applied to the sampled electrical signal in order to equalize the frequency response of a transmission set further comprises: selecting (122) a sub-part (FJ) of the filter (F) comprising a specific parameter having an associated value in a time impulse response of the filter that is the highest among the respective values ​​of the parameters of the filter (F) in that impulse response; and wherein the selected sub-part (Fi) of the filter (F) (122) corresponds to the filter (h[k]) to be applied to the sampled electrical signal in order to equalize the frequency response of the transmission set.

8. Data processing device (6) comprising a processing circuit (PROC) for implementing the method according to any one of claims 1 to 7.