DEVICE FOR CONNECTING, BY REALLOCATION OF TRANSMISSION CHANNELS, TO AN ON-BOARD PASSIVE FIBRE MULTIPLEXED COMMUNICATION NETWORK FOR AN AIRCRAFT

Abstract

A device for connection to an on-board multiplexed network of communication by multi-mode optical fibers for an aircraft, the device comprising a first optical component for modifying the spatial profile of a light beam, comprising a multi-mode optical input terminal configured to be connected to a first multi-mode optical fiber and single-mode optical output terminals, and a second optical component for modifying the spatial profile of a light beam, comprising single-mode optical input terminals and a multi-mode optical output terminal configured to be connected to a second multi-mode optical fiber. It further comprises an optical harness for switching and reassigning a transmission channel including single-mode optical inputs coupled to the single-mode optical output terminals of the first component, single-mode optical outputs coupled to the single-mode optical input terminals of the second optical component, and single-mode waveguides.

Claims

1. A device for connection to an on-board multiplexed network of communication by multi-mode optical fibers, intended to be mounted onboard an aircraft, the connection device comprising: a first optical component for modifying the spatial profile of a light beam, comprising a multi-mode optical input terminal configured to be connected to a first multi-mode optical fiber and single-mode optical output terminals, and a second optical component for modifying the spatial profile of a light beam, comprising single-mode optical input terminals and a multi-mode optical output terminal configured to be connected to a second multi-mode optical fiber-, wherein that it further comprises an optical harness for switching and reassigning a transmission channel including single-mode optical inputs coupled to the single-mode optical output terminals of the first component, single-mode optical outputs coupled to the single-mode optical input terminals of the second optical component, and a plurality of single-mode waveguides connected at a first end to an input of the optical harness and/or at a second end to an output of the optical harness, the first optical component for modifying the spatial profile of a light beam and the second optical component for modifying the spatial profile of a light beam being passive optical components configured to perform Spatial Division Multiplexing or Spatial Division Demultiplexing via Multi-Plane Light Converter.

2. The connection device according to claim 1, wherein the single-mode waveguides of the optical harness are made of silica.

3. The connection device according to claim 1, wherein the optical harness further comprises a control module and controlled optical switches configured to change their configuration depending on the command received from the control module, each controlled optical switch making it possible to modify the output to which the input associated with the controlled switch is optically connected.

4. The connection device according to claim 1, wherein the optical harness is removable from the connection device to be replaced at any time by another optical harness of a possibly different configuration.

5. An on-board optical communication network adapted to allow data transmission by multi-mode optical fiber between pieces of equipment of an aircraft, the network comprising an upstream multi-mode optical fiber intended to be coupled to a source of a light radiation digitally modulated by the information and a downstream multi-mode optical fiber intended to be coupled to a receiver making it possible to demodulate this information, wherein that it comprises at least one connection device according to claim 1 connected between the upstream optical fiber and the downstream optical fiber.

6. An aircraft comprising at least one on-board optical communication network according to claim 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The invention will be better understood upon reading the following, as indication but without limitation, with reference to the appended drawings in which:

[0061] FIG. 1, already described, schematically presents a data distribution network known from the prior art.

[0062] FIG. 2, already described, schematically illustrates an example of transmission in a first direction on a Coarse Wavelength Division Multiplexed optical line of the prior art.

[0063] FIG. 3, already described, schematically illustrates an example of transmission in a second direction opposite to the first direction, on a Coarse Wavelength Division Multiplexed optical line of the prior art.

[0064] FIG. 4, already described, schematically presents a hypothetical Wavelength Division Multiplexed optical network according to the prior art.

[0065] FIG. 5 schematically represents an optical component for modifying the spatial profile of a light beam according to one embodiment of the invention,

[0066] FIG. 6 schematically represents an optical communication network comprising a connection device according to one embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

[0067] The spatial profile of a light beam is a distribution profile of the electric field in a light beam section transverse to the axis of propagation. It is a profile of complex amplitudes of an electric field which can be represented at all points of the section by a strength y and a phase. For example, the strength profile would be a Gaussian in the case of a beam transmitted by a single-mode fiber excited according to the fundamental mode. The profile is obviously more complex in the case of a multi-mode beam and it can be broken down into specific profiles corresponding to each mode.

[0068] The propagation modes in a multi-mode fiber are commonly listed in the literature and often designated by letters and numbers that indicate the nature of the mode and its order along two dimensions. Typically, the first-order mode or fundamental mode is commonly referred to as LP01, the higher modes are the LP11a, LP11b, LP21a, LP11b, LP02, LP03, LP31a, LP31b modes, etc.

[0069] Any beam propagating in a multi-mode fiber can be broken down based on the LP modes. The technical literature abundantly gives the shapes of these spatial profiles for the most common modes. The most rapidly propagating mode is the fundamental LP01 mode. The other modes propagate more slowly, first the LP11 mode, then the LP02 and LP21 modes, and then the other modes. It is for example possible to choose to divide these modes into a first group comprising only the LP01 mode and a second group comprising the LP11, LP02 and LP21 modes. Or it is possible to divide the two modes into a first group comprising the LP01 mode and the LP11 mode and a second group comprising the LP02 and LP21 modes. A division of the modes of the fiber into more than two groups is possible.

[0070] In the article by Jean-Franois Morizur and others, Programmable 10 unitary spatial mode manipulation in the Journal of Optical Society of America Vol. 27, No 11, November 2010, it is shown that it is possible to transform the spatial profiles of a family of light beams into any other family of spatial profiles, provided that the transformation thus defined conserves energy, by a succession of intermediate transformations in free (unguided) space each using a matrix of phase shifting elements acting on the section of the light beam which illuminates this matrix. In this article, the phase shifting elements are programmable and constituted by electrically actuatable deformable mirrors but the principle would be the same with a non-programmable mirror plate structured with a fixed configuration for a predefined transformation. It would also be the same with a programmable (liquid crystals) or non-programmable transparent plate, structured to introduce a phase shift matrix on the path of the light beam.

[0071] This article also shows how any unitary transformation (which conserves energy) of the spatial beam profile can be obtained exactly by using a finite number of intermediate transformations obtained by an alternation of phase shifting structures and optical Fourier transformations. If a limit (for example around ten) is imposed on the number of intermediate transformations, the overall transformation obtained will be more approximate. The phase shifting structures modify the phases in the section of the light beam point by point. The optical Fourier transforms can be spherical lenses or mirrors, but in practice a simple propagation of the beam over a few centimeters in free space between two phase shifting structures can replace the optical Fourier transforms in the alternation.

[0072] The previous article gives a recipe for the design of optical systems based on a succession of phase shifting structures and free propagation between these structures to perform any unitary transformation of the spatial profile of a coherent light beam.

[0073] Another design recipe for the different sets of phase shifting structures making it possible to make a desired transformation has been described in the patent publication WO 2012/085046, either to correct a beam that has undergone a profile transformation or to voluntarily apply a desired profile transformation to a beam. This design of the different phase shifting structures, which is faster, more efficient but less general than that of the previous article, is done in practice by simulation in a computer capable of modeling the behavior of the beam profiles in a succession of different optical elements and in particular of the phase shifting structures and free propagation spaces. The computer simulates the passage, through this succession of optical elements, of a light beam having an input profile and it calculates the resulting output beam. It then causes this output beam to interfere with a beam having a desired spatial profile on the plane corresponding to a phase shifting structure. The result of the interferences on the plane corresponding to each phase shifting structure is observed and the configuration of the structure is modified in a direction tending to maximize the interferences. This operation is repeated on the successive phase shifting structures and we start again with successive iterations on all the structures until obtaining an output beam with a profile very close to the desired beam. The final configuration of the phase shifting structures obtained after these iterations is then used to constitute the optical component for modifying the spatial profile which transforms the first profile into a second desired profile, whatever it may be.

[0074] Transformations consisting of a multiplexing of several propagation modes, that is to say a transformation of the spatial profile of several simple modes into a complex mode combining the spatial profiles of the simple modes, have been proposed in the article by Guillaume Labroille and others, Efficient and mode-selective spatial mode multiplexer based on multi-plane light conversion, in Optics Express 30 Jun. 2014 Vol. 22 No 13 p. 15599.

[0075] The component that performs this transformation also allows performing the inverse transformation (demultiplexing). Rather than using a succession of phase shifting structures separated by free propagation spaces, it uses multiple reflection of the beam between two mirrors and a passage of the beam each time through the same phase shifting structure but in portions different therefrom, each portion representing the equivalent of a particular phase shifting structure.

[0076] The optical component used in the present invention is a spatial profile transformation component made according to the principles just described. It executes a transformation of the spatial profiles corresponding to several propagation modes or mode groups, each profile being transformed into another profile, in particular to transform the single-mode signals into a multi-mode signal or conversely.

[0077] To explain the operation of the optical component for modifying the spatial profile, a simplified example of a way of carrying out the invention in the case where the input beam only include two modes LP01 (fast) and LP11a (slow) can be given. Such an example beam may have been obtained by prior filtering eliminating all the other modes. We are therefore looking for the succession of phase deformations that will make it possible to simultaneously transform in the optical component the profile of the light entering the LP01 mode towards the LP11a mode and the profile of the light entering the LP11a mode towards the LP01 mode. To find the relevant succession of deformations, it is possible to use the iterative method described above or the method described in the aforementioned article by JF Morizur. The LP01 mode carrying information which was slightly in advance due to the propagation, in the input fiber(s), of the optical component has become an LP11a mode carrying this information in advance and reciprocally the LP11a mode carrying slightly delayed information has become a faster LP01 mode but carrying delayed information. In the propagation in the output fiber(s), the LP11a mode will lose the lead it had taken at the input and the LP01 mode will catch up the delay it had taken. If the fibers are identical, they should be preferably given identical lengths. If they are not identical, that is to say if they do not give the same propagation delay differences, it is necessary to calculate the optimal position of the component to place it where the delay differences due to the input fiber are equal to the delay differences due to the output fiber.

[0078] FIG. 5 schematically illustrates an example of architecture of an optical component 50 for modifying the spatial optical profile of a light beam according to one embodiment of the invention.

[0079] The optical component 50 comprises a first multi-mode terminal 53 to which is connected a multi-mode optical fiber 51 which provides a beam F modulated in amplitude by digital information, second single-mode terminals 54 to which are connected single-mode optical fibers 52, a pair of mirrors 55 and 56, and a structure 57 of optical phase shifting of the beam. The first terminal and the second terminals are preferably systems including lenses.

[0080] In a first direction of use of the optical component 50, the beam F is delivered as input to the first multi-mode terminal 53 of the optical component 50 by the multi-mode optical fiber 51. The beam F is then directed onto a pair of mirrors 55, 56, optionally passing through optical elements such as lenses, reflective mirrors, semi-transparent mirrors. The optical phase shifting structure 57 is made on the reflective surface of the first mirror 55, and the pair of mirrors 55 and 56 ensures the multiple reflections of the beam.

[0081] The optical phase shifting structure 57 is formed on the reflective surface of the first mirror 55. Indeed, the first mirror 55 comprises, on the scale of the wavelength of the radiation, a reflective surface having a relief whose hollows and bumps define by their heights and depths the relative phase shifts to be applied to the beam parts that strike these hollows and bumps. These heights and depths relative to an average plane are of the order of the wavelength of the light beam, ranging from a fraction of a wavelength to a few wavelengths. A use wavelength could be 1,550 nm.

[0082] The first mirror 55 thus plays here not only the role of a mirror to ensure multiple paths of the beam but also the role of a structure of optical phase shifting of the beam. The multimodal beam is thus transformed, over the successive phase shifts, into a set of single-mode light beams at the output of the mirror pair 55 and 56. The light beams Fs are directed at the output towards the second single-mode terminals 54 before being each added into a single-mode optical fiber 52.

[0083] The optical component 50 operates in both directions. In the opposite direction, the first multi-mode terminal 53 is an output terminal and the second terminals 54 are input terminals.

[0084] FIG. 6 schematically represents a multiplexed optical data communication network 30 according to one embodiment of the invention.

[0085] The optical network 30 comprises an optical source S digitally modulated by information to be transmitted and an optical receiver R making it possible to decode the transmitted digital information. In the simplified example illustrated in FIG. 6, the optical network 30 further comprises two connection devices 40 connected in series between the source S and the receiver R.

[0086] The source S is connected to a first connection device 40 via an optical component 50s for modifying the spatial profile and a first multi-mode optical fiber 31, and the receiver is connected to a second connection device 40 via an optical component 50r for modifying the spatial profile via a second multi-mode optical fiber 32. And the first connection device 40 is coupled to the second connection device 40 via a third multi-mode optical fiber 33.

[0087] Each connection device 40 comprises a first optical component 50a configured to be connected to a multi-mode optical fiber on its multi-mode input terminal 53a and deliver single-mode light beams on its single-mode output terminals 54a, a second optical component 50b configured to receive single-mode optical beams on its single-mode inputs 54b and be connected to a multi-mode optical fiber on its multi-mode output 53b, and an optical harness 60 for switching and reassigning the transmission channel coupled between the single-mode output terminals 54a of the first optical component 50a and the single-mode input terminals 54b of the second optical component 50b.

[0088] The optical harness 60 comprises a plurality of single-mode optical fibers 61 made of silica in the case of SDM, and one or several terminals for fibers, also called connectors, to allow the replacement of the harness. The harness 60 can comprise different coupling configurations between its input and output connectors, these couplings can comprise couplings to additional inputs to allow the connection to a new optical fiber thus allowing the connection of a new subscriber to the optical network, or conversely, a lack of coupling of an input to one of the outputs, or conversely.

[0089] Depending on the desired architecture and therefore following the desired configuration, the optical harness 60 ensures the routing of the different optical signals on the transmission channels available among the multi-mode fibers 31 of the optical network 30. The routing is determined by the progress of the optical fibers used between the two optical components 50 which carry out the spatial profile modification. The optical fibers 61 are added according to the desired particular arrangement in the terminals 54.

[0090] The optical channel reassignment harness 60 can be presented in two different forms. For example, it could be considered as a single component because it is made up of secured and inseparable elements. The optical harness 60 fixed in a specific configuration is identified with a unique reference. In such a case, in the event of a search for a new routing solution, it is the entire harness with its connector(s) at the ends that should be replaced by another harness meeting the reconfigurability need.

[0091] In this configuration, the optical harness 60 in fixed configuration can thus be made with an MPO type multi-fiber harness meeting the IEC 61754-7 standard with high-density optical contacts. Indeed, after mounting of the contacts on the multi-fiber harness, it is not possible to modify the arrangement of the fibers.

[0092] Conversely, in another configuration, the optical harness 60 could be scalable and modifiable. To this end, the fibers are independent of each other and can be easily manipulated in order to be able to drop or add each of the contacts at their ends into the dedicated cavity of the terminal 54. Thus, the contacts in question could be of the type called snap or push-pull type. Mention can be made on the one hand to the contacts conventionally used in the aeronautical field such as the ELIO (EN4531) or Luxcis (ARING 801) contact which can for example be associated with MIL 38999 or EN4165 or ARINC600 type connectors, without forgetting on the other hand the conventional telecom contacts such as the Lucent Connector (LC) meeting the IEC 61754-20 standard and or the Switching Connector (SC) meeting the IEC 61754-4 standard.