Intradyne detection device

Abstract

The invention relates to an intradyne detection device (1) comprising a laser emitter (11) configured to emit an initial optical beam (FOI), a coupler (12) configured to receive the initial optical beam (FOI) as input and to produce a first optical beam (FO1) and a second optical beam (FO2) as output, the first and second optical beams having the same frequency spectrum as the initial optical beam, an optical component (13) configured to receive the second optical beam (FO2) and to produce a third optical beam (FO3) as output, the frequency spectrum of the third optical beam (FO3) being frequency-shifted relative to the frequency spectrum of the second optical beam (FO2) by a predetermined shift, and an intradyne receiver (14) configured to receive, at a first input (E1), an optical communication signal carried by the first optical beam (FO1) and, at a second input (E2), a local oscillator signal, the local oscillator signal being generated by the optical component (13) and carried by the third optical beam (FO3).

Description

[0001] DESCRIPTION

[0002] TITLE: Intradyne detection device

[0003] The present invention relates to the field of intradyne sensing, and in particular intradyne sensing configured to control phase and frequency residuals at the output of the intradyne receiver.

[0004] It is known to use two separate lasers to emit both a telecommunications signal and a local oscillator signal. In intradyne detection requires two waves with similar frequencies. However, lasers are subject to instabilities, such as frequency hopping, which are highly dependent on the environment and the current control sources. To avoid detection penalties during digitization, it is known to use two very complex control systems to keep the instabilities of each laser under control. Furthermore, for metrological purposes, it is useful to know the frequency difference between the telecommunications wave and the local oscillator as precisely as possible.

[0005] The invention therefore aims to provide a simple solution to all or part of these problems.

[0006] To this end, the present invention relates to an intradyne detection device comprising:

[0007] - a laser emitter configured to emit an initial optical beam, - a coupler configured to receive said initial optical beam as input and to produce as output a first optical beam and a second optical beam, the first and second optical beams having the same frequency spectrum as the initial optical beam,

[0008] - an optical component configured to receive the second optical beam and to produce a third optical beam at output, the frequency spectrum of the third optical beam being shifted in frequency relative to the frequency spectrum of the second optical beam according to a predetermined shift,

[0009] - an intradyne receiver configured to receive on a first input an optical communication signal carried by the first optical beam and on a second input a local oscillator signal, the local oscillator signal being created by the optical component and carried by the third optical beam.

[0010] According to these provisions, the device allows the output of the intradyne receiver to produce an electrical signal with a signal-to-noise ratio very close to that of the optical communication signal carried by the first optical beam. In other words, the device's local oscillator does not introduce any measurable analog penalty. The device therefore allows for precise control of the phase and frequency residuals that typically interfere with the evaluation of modulating components and the intradyne detector. The device is thus suitable for integration into a test bench for modulating components and intradyne detectors intended for optical communications.

[0011] According to one embodiment, the invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0012] According to one embodiment, the coupler is configured to produce at the output the first optical beam having a power equal to 50% of the power of the initial optical beam and a second optical beam having a power equal to 50% of the power of the initial optical beam.

[0013] According to one embodiment, the optical component is an acousto-optic modulator. According to one embodiment, the acousto-optic modulator is polarized with a radio-frequency wave generator generating a wave at the resonance frequency of the acousto-optic modulator.

[0014] According to an example of an embodiment, the frequency shift generated by the acousto-optic modulator is between 20 and 60 MHz, preferably between 30 and 50 MHz, preferably equal to 40 MHz.

[0015] According to one example of implementation, the laser emitter is a RIO type laser.

[0016] According to one embodiment, the intradyne detection device further includes a modulator configured to receive and modulate the first optical beam with the optical communication signal, and to produce at output said optical communication signal carried by the first optical beam.

[0017] According to one example implementation, the modulation is of the QPSK type.

[0018] According to one aspect, the invention also relates to a method for controlling and reducing a frequency difference between an optical communication signal and a local oscillator signal, the method comprising the following steps:

[0019] - to emit, via a laser emitter, an initial optical beam,

[0020] - to receive, at an input of a coupler, said initial optical beam in order to produce, at the output of said coupler, a first optical beam and a second optical beam, the first and second optical beams having the same frequency spectrum as the initial optical beam,

[0021] - receive, on an input of an optical component, the second optical beam, to produce, at the output of said optical component, a third optical beam, the frequency spectrum of the third optical beam being shifted in frequency relative to the frequency spectrum of the second optical beam according to a predetermined shift, - receive, on a first input of an intradyne receiver the optical communication signal carried by the first optical beam, and on a second input of the intradyne receiver the local oscillator signal, the local oscillator signal being created by the optical component and carried by the third optical beam.

[0022] According to one embodiment, the process further includes a step of modulating the first optical beam by a modulator configured to receive and modulate the first optical beam with a modulation signal generated by the modulator, and to produce at output said optical communication signal carried by the first optical beam.

[0023] According to one aspect, the invention relates to a test bench configured for evaluating an optical link between an intradyne transmitter and receiver, the test bench comprising an optical device according to one of the embodiments previously described, in which the optical link is ensured by the optical communication signal carried by the first optical beam emitted by the laser transmitter of the device and received by the intradyne receiver of the device on its first input.

[0024] According to these provisions, the test bench allows the output of the intradyne receiver to produce an electrical signal with a signal-to-noise ratio very close to that of the optical communication signal carried by the first optical beam. Indeed, the device's local oscillator does not introduce any measurable analog penalty. The test bench thus allows for precise control of the phase and frequency residuals that typically interfere with the evaluation of modulating components and the intradyne detector. The test bench is therefore suitable for evaluating modulating components and intradyne detectors intended for use in optical links. For a better understanding, an embodiment and / or implementation of the invention is described with reference to the attached drawings, which represent, by way of non-limiting example, an embodiment or implementation of a device and / or method according to the invention.The same references on the drawings designate similar elements or elements whose functions are similar.

[0025] [Fig. 1] is a simplified representation of a device according to one embodiment of the invention

[0026] [Fig. 2] is a schematic representation of a sequence of steps of a process according to an implementation method of the invention.

[0027] Traditionally, two separate lasers are used to emit both the telecommunications signal and the local oscillator. In intradyne detection requires two waves with similar frequencies. However, lasers are subject to instabilities, such as frequency hopping, and these instabilities are highly dependent on the environment and the current control sources. To avoid detection penalties during digitization, two very complex control systems are often used to keep the instabilities of each laser under control. This invention eliminates the need for these complex control systems. Furthermore, for metrology and evaluation purposes of the modulating components and / or the intradyne detector, it is necessary to know, as precisely as possible, the frequency difference between the telecommunications wave and the local oscillator, and to control this difference.

[0028] In order to finely control the phase and frequency residuals that usually disrupt the evaluation of the modulating components and the intradyne detector, the intradyne detection device 1 according to the invention comprises:

[0029] - a laser emitter 11 configured to emit an initial optical beam FOI, - a coupler 12 configured to receive said initial optical beam FOI as input and to produce as output a first optical beam FO1 and a second optical beam F02, the first and second optical beams having the same frequency spectrum as the initial optical beam,

[0030] - an optical component 13 configured to receive the second optical beam FO2 and to produce at output a third optical beam FO3, the frequency spectrum of the third optical beam FO3 being shifted in frequency relative to the frequency spectrum of the second optical beam FO2 according to a predetermined shift,

[0031] an intradyne receiver 14 configured to receive on a first input E1 an optical communication signal carried by the first optical beam FO1 and on a second input E2 a local oscillator signal, the local oscillator signal being generated by the optical component 13 and carried by the third optical beam FO3.

[0032] According to these provisions, the intradyne detection device 1 according to the invention makes it possible to obtain at the output of the intradyne receiver an electrical output signal with a signal-to-noise ratio very close to the signal-to-noise ratio of the optical communication signal carried by the first optical beam. In other words, the local oscillator of the device does not induce any measurable analog penalty. The device therefore makes it possible to finely control the phase and frequency residuals that usually interfere with the evaluation of modulating components and the intradyne detector. The device is therefore suitable for integration into a test bench for modulating components and intradyne detectors intended for implementing optical communications.

[0033] According to one embodiment, the coupler 12 is configured to produce at its output the first optical beam FO1 having a power equal to 50% of the power of the initial optical beam FOI and a second optical beam FO2 having a power equal to 50% of the power of the initial optical beam FOL

[0034] According to a particular embodiment, the optical component 13 is an acousto-optic modulator 13. More specifically, the acousto-optic modulator 13 is biased with a radio-frequency wave generator producing a wave at a resonant frequency of the acousto-optic modulator. For example, the frequency shift generated by the acousto-optic modulator is between 20 and 60 MHz, preferably between 30 and 50 MHz, preferably equal to 40 MHz.

[0035] According to one example of implementation, the laser emitter is a RIO type laser.

[0036] In particular, a polarization-maintaining isolator is positioned between the laser 11, immediately after the laser output, to protect it, so as to attenuate any optical wave whose propagation is contrary to its own direction.

[0037] The device 1 further comprises, for example, a modulator 15 configured to receive and modulate the first optical beam FO1 with the optical communication signal, and to output said optical communication signal carried by the first optical beam FO1. Said modulator 15 can thus be evaluated, under appropriate conditions, by the intradyne detection device 1 according to the invention. The modulator can, for example, produce QPSK-type modulation.

[0038] The invention also relates to a method 100 for controlling and reducing a frequency difference between an optical communication signal and a local oscillator signal, the method 100 comprising the following steps:

[0039] - emit 101, by a laser emitter 11, an initial optical beam FOI, - receive 102, on an input of a coupler 12, said initial optical beam FOI to produce, at the output of said coupler 12, a first optical beam FO1 and a second optical beam FO2, the first and second optical beams having the same frequency spectrum as the initial optical beam, - receive 103, on an input of an optical component 13, the second optical beam FO2, to produce, at the output of said optical component 13, a third optical beam FO3, the frequency spectrum of the third optical beam FO3 being shifted in frequency with respect to the frequency spectrum of the second optical beam FO2 according to a predetermined shift,

[0040] receive 104, on a first input E1 of an intradyne receiver 14 the optical communication signal carried by the first optical beam FO1, and on a second input E2 of the intradyne receiver 14 the local oscillator signal, the local oscillator signal being carried by the third optical beam FO3.

[0041] Optionally, the process 100 further includes a modulation step 103 bis of the first optical beam by a modulator 15 configured to receive and modulate the first optical beam FO1 with a modulation signal generated by the modulator 15, and to produce at output said optical communication signal carried by the first optical beam FO1.

[0042] According to one aspect, the invention relates to a test bench configured for the evaluation of an optical link between an intradyne transmitter and receiver, the test bench comprising an optical device 1 according to one of the embodiments previously described, in which the optical link is ensured by the optical communication signal carried by the first optical beam FO1 emitted by the laser transmitter of the device 1 and received by the intradyne receiver 14 of the device 1 on its first input E1.

Claims

DEMANDS 1. Intradyne detection device (1) comprising: - a laser emitter (11) configured to emit an initial optical beam (FOI), - a coupler (12) configured to receive as input said initial optical beam (FOI) and to produce as output a first optical beam (FO1) and a second optical beam (FO2), the first and second optical beams having the same frequency spectrum as the initial optical beam, - an optical component (13) configured to receive the second optical beam (FO2) and to produce as output a third optical beam (FO3), the frequency spectrum of the third optical beam (FO3) being shifted in frequency relative to the frequency spectrum of the second optical beam (FO2) according to a predetermined shift, - an intradyne receiver (14) configured to receive on a first input (E1) an optical communication signal carried by the first optical beam (FO1) and on a second input (E2) a local oscillator signal, the local oscillator signal being created by the optical component (13) and carried by the third optical beam (FO3).

2. Device according to claim 1, wherein the optical component (13) is an acousto-optic modulator.

3. Device according to any one of claims 1 or 2, further comprising a modulator (15) configured to receive and modulate the first optical beam (FO1) with the optical communication signal, and to produce at output said optical communication signal carried by the first optical beam (FO1).

4. Device according to claim 1, wherein the modulation is of the QPSK type.

5. Method (100) for controlling and reducing a frequency difference between an optical communication signal and a local oscillator signal, the method (100) comprising the following steps: - emit (101), by a laser emitter (11), an initial optical beam (FOI), - receive (102), on an input of a coupler (12), said initial optical beam (FOI) to produce, at the output of said coupler (12), a first optical beam (FO1) and a second optical beam (FO2), the first and second optical beams having the same frequency spectrum as the initial optical beam, - receive (103), on an input of an optical component (13), the second optical beam (FO2), to produce, at the output of said optical component (13), a third optical beam (FO3), the frequency spectrum of the third optical beam (FO3) being shifted in frequency with respect to the frequency spectrum of the second optical beam (FO2) according to a predetermined shift, - receive (104), on a first input (E1) of an intradyne receiver (14) the optical communication signal carried by the first optical beam (FO1), and on a second input (E2) of the intradyne receiver (14) the local oscillator signal, the local oscillator signal being created by the optical component (13) and carried by the third optical beam (FO3).

6. Method (100) according to claim 5, further comprising a modulation step (103bis) of the first optical beam by a modulator (15) configured to receive and modulate the first optical beam (FO1) with a modulation signal generated by the modulator (15), and to produce at output said optical communication signal carried by the first optical beam (FO1).

7. Test bench configured for evaluating an optical link between an intradyne transmitter and receiver, the test bench comprising an optical device (1) according to any one of claims 1 to 4, wherein the optical link is ensured by the optical communication signal carried by the first optical beam (FO1) emitted by the laser transmitter of the device (1) and received on its first input (E1) by the intradyne receiver (14) of the device (1).

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