The invention relates to the field of equipment for communications networks, and more particularly to optical multiplexer devices for inserting/dropping multiplexed optical resources of the kind used for equipping certain pieces of equipment when they constitute network nodes.
The term “optical resources” is used herein to mean both wavelengths and wavelength bands.
Transferring multiplexed optical resources within a network is an operation that is complex. It frequently requires some information or resources to be inserted or dropped into or from resources that are being transferred, and this can happen at various levels. Such insertion and/or dropping generally takes place in network equipment, such as routers, constituting nodes of a network. More precisely, insertion and/or dropping is performed using optical multiplexer devices for inserting/dropping multiplexed optical resources, which devices are connected to incoming and outgoing optical fibers of an optical transmission line in which the optical resources are traveling.
Such devices are connected directly or via an optical amplifier to the incoming optical fiber (or upstream fiber).
Some such devices comprise firstly an optical coupler used for taking a fraction of the wavelength division multiplexed signal from the outlet of the incoming fiber in order to transfer said fraction via an outlet to a first demultiplexer of the 1 to N type delivering demultiplexed resources on N outlets. Access to resources that are to be processed locally, e.g. for the purpose of receiving the data they contain or for regenerating the data, takes place via said outlets. The other outlet from the coupler feeds an optical system used for allowing those resources that need to be forwarded to the outgoing optical fiber to transit through the equipment. The other resources are blocked by the device. The device is generally constituted by a demultiplexer, with each of its outlets connected to an optical attenuator module, e.g. of the variable optical attenuator (VOA) type, and a multiplexer for grouping together the resources. The resources as regrouped in this way are then forwarded to the first inlet port of a second coupler whose second inlet port is used for adding in new resources that have previously been grouped together by another multiplexer. The outlet port from said second coupler then feeds the outgoing optical fiber either directly or via an amplifier.
Because such devices comprise four multiplexer or demultiplexer components, they are expensive and bulky. In addition, such devices lead to high insertion losses between the incoming fiber and the outgoing fiber which can degrade the resources even when optical amplifier modules are used on either side of the device.
In order to attempt to improve the situation, several solutions have been proposed. Amongst such solutions, mention can be made in particular of that described in patent document GB 2 381 683.
That solution consists in providing a device that comprises:
Such a device does indeed make it possible to use only two demultiplexer or multiplexer components, but it requires firstly that each channel should be associated with three light guide portions, which is bulky, and secondly that each portion should be fitted with an amplifier module such as a semiconductor optical amplifier (SOA), which can be expensive both at manufacture and during maintenance.
No known solution provides full satisfaction and the invention thus seeks to improve the situation.
To this end, the invention provides an optical multiplexer device for inserting/dropping multiplexed optical resources for an optical transmission line comprising at least an incoming optical fiber and an outgoing optical fiber, the device comprising firstly first coupler means having an inlet and an outlet connected respectively to the incoming and outgoing optical fibers, and an inlet/outlet coupled to said inlet and to said outlet, and secondly both-way multiplexer/demultiplexer means comprising a primary inlet/outlet coupled to the inlet/outlet of the first coupler means, and at least two secondary inlets/outlets, and defining at least two internal channels connected to the primary inlet/outlet and to the secondary inlets/outlets.
That optical device is characterized by the fact that it includes at least two send and/or receive modules each coupled to a secondary inlet/outlet by both-way light guide means, the modules being fitted with optical processor means connected in series and capable, on order, of placing themselves in a selected one of at least a reflection state for reflecting an optical resource towards the secondary inlet/outlet that delivers it, and a transmission state for enabling an optical resource to be transferred (inserted or dropped) between a send and/or receive module and the secondary inlet/outlet to which it is coupled.
The term “send and/or receive module” is used herein to mean either a send module, or a receive module, or indeed a module subdivided into a send module and a receive module.
The device of the invention may include other characteristics that can be taken separately or in combination, and in particular:
The invention is particularly well adapted, although not exclusively, to the field of optical communications, in particular when the optical resources are wavelengths or wavelength bands.
Other characteristics and advantages of the invention appear on examining the following detailed description and the accompanying drawings, in which:
The accompanying drawings contribute not only to describing the invention, but may also contribute to defining it, where appropriate.
The invention seeks to enable optical resources to be inserted and dropped into and from an optical transmission line belonging to a communications network, for example.
Reference is made initially to
In the description below, it is assumed that the optical resources that are inserted and dropped are wavelengths, however they could equally well be wavelength bands.
The device D shown comprises firstly first coupler means C1 comprising an inlet and an outlet connected respectively to the incoming optical fiber F1 and the outgoing optical fiber F2, and also an inlet/outlet 1 coupled to its inlet and outlet. The first coupler means C1 is implemented in this case in the form of an optical circulator.
The device D also comprises both-way multiplexer/demultiplexer means 2 comprising in particular a first primary inlet/outlet ES11 coupled to the inlet/outlet 1 of the optical circulator C1.
These both-way multiplexer/demultiplexer means 2 serve both to demultiplex and to multiplex optical resources. These means are constituted by an optical multiplexer and demultiplexer (OMAD), e.g. implemented in the form of a wavelength selector of the arrayed waveguide grating (AWG) type.
Such an OMAD 2 defines at least two internal channels 3, each connected firstly to its first primary inlet/outlet ES11 and secondly to a respective one of its secondary inlets/outlets ES2. Each internal channel 3 is arranged in such a manner as to enable optical resources presenting a selected wavelength to be demultiplexed and/or multiplexed.
In the example shown, each inlet/outlet ES2i (in this case i=1 to 4, but i could take any value greater than or equal to 2) of the OMAD 2 is coupled to light guide means 4i (represented by a one-way or a both-way arrow) fitted with optical processor means 5i and 6i and coupled to a receive module Ri. These light guide means 4i are of the both-way type in this case. They are preferably implemented in the form of optical fibers, but they could also be devised differently, and in particular in the form of planar waveguides.
In this case, each waveguide 4i is fitted with two optical processor means 5i and 6i connected in series and arranged in such a manner as to be capable together of defining at least two states: a reflection state for reflecting an optical resource towards the secondary inlet/outlet ES2i that delivered it, and a transmission state enabling an optical resource to be conveyed (or transferred) from the secondary inlet/outlet ES2i that delivered it to one of the receive modules Ri with which it is coupled.
For example, and as shown diagrammatically, each first optical processor means 5i is a (first) reflector means presenting a capacity for reflection that is adjustable as a function of configuration orders (or instructions or signals). By way of example, it can be implemented in the form of a micro-electromechanical system (MEMS) comprising a variable-position mirror capable of occupying at least a total reflection position (to reflect the signals for returning to the outgoing fiber F2), a position of partial and adjustable reflection and/or transmission (for reflection with attenuation), and a total transmission position (for transmission without attenuation to the receiver Ri). This sliding mirror can be housed in a space formed between two waveguide portions 4i, so as to be capable of obstructing the sections thereof, in full, in part, or not at all.
In this case, each (optional) second optical processor means 6i serves to co-operate with the associated reflector means 5i in order to block the residual signal coming from partial reflection (in said first reflector means 5i), thereby defining the state of reflection with attenuation. For example, it can be implemented in the form of a second reflector means, such as a MEMS capable of taking a total shut-off position and a total transmission position. For example, in the total shut-off position, the light signals are reflected in a direction which prevents them from being reintegrated in the light guide means 4.
In the configuration shown in
In a variant, and as shown in
Furthermore, as shown in
The second primary inlet/outlet ES12 is also coupled to the outgoing optical fiber F2 downstream from the circulator C1 by another light guide means 11 and a second coupler means C2. In this case the light guide means 11 is of the one-way type. It is preferably implemented in the form of an optical fiber. In this case the second coupler means C2 is implemented in the form of an optical Y coupler, i.e. it constitutes a 2 to 1 type coupler.
In this case, each waveguide 9j is fitted with optical processor means 10j arranged to be capable of defining at least two states: a total shut-off state for blocking any optical resource sent by the send module Tj; and a total transmission state enabling an internal channel 7j to be fed with the optical resource.
By way of example, and as shown diagrammatically, each optical processor means 10j is implemented in the form of a “shutter” means such as a MEMS comprising a variable-position shutter capable of occupying a total shut-off position and a total transmission position.
In the configuration shown in
Reference is now made to
In this case, the OMAD 2 has only one series i of both-way internal channels 3i (in this case i=1 to 4, but i could have any value greater than or equal to 2), each channel being connected firstly to its first (and sole) primary inlet/outlet ES1 which in turn is connected to the inlet/outlet 1 of the circulator C1, and secondly to one of its secondary inlets/outlets ES2i. Furthermore, each secondary inlet/outlet ES2i is coupled to a send and receive module Mi, constituted by a receive module Ri and a send module Ti, e.g. two juxtaposed modules, via both-way type light guide means 4′ and 12.
By way of example, the light guide means 12 is a Y coupler connected firstly to one end of the guide means 4′ and secondly to the send module Ti and to the receive module Ri. However, in a variant, the light guide means 12 may be implemented in the form of planar waveguide portions or indeed in the form of a circulator provided with an inlet/outlet connected to the waveguide 4′, an outlet connected to the receive module Ri, and an inlet connected to the send module Ti.
Where necessary, this embodiment makes it possible not only to attenuate the reflected or dropped (for sending to a receive module Ri) light signals to be attenuated, but also enables those resources that are to be inserted into the optical fiber FO to be attenuated.
In this case, the optical processor means 5 and 6′ are fitted to the portions 4′ of the light guide means, e.g. implemented in the form of planar technology waveguides.
In this case the second optical processor means 6′ are preferably implemented in the form of VOA type means, like the variant shown in
In the configuration shown in
As shown in
This configuration is advantageous since it enables a signal to be forwarded to the receive module Ri at a power that does not depend on the attenuation applied by the attenuator 6′i to the resources sent by the send module Ti.
Naturally, other variants could be envisaged in which each second portion 15i and each third portion 16i is fitted with its own processor means.
Reference is made to
In this case, the device D is arranged so as to enable optical resources coming from or going to two pairs (a and b) of incoming optical fibers (F1a, F1b) and outgoing optical fibers (F2a, F2b) to be inserted and dropped using a single OMAD 2. For this purpose, it has two examples of the elements of the second embodiment and an adaptive OMAD 2 which defines internal channels 3a and 3b for inserting/dropping optical resources respectively in the first optical fibers (a) and the second optical fibers (b).
More precisely, the OMAD 2 has a first primary inlet/outlet ES1a connected to a first circulator Ca (or the equivalent) and to i internal channels 3ai (in this case i=1 to 4, but i could have any value greater than or equal to 2), and a second primary inlet/outlet ES1b connected to a second circulator Cb (or the equivalent) and to k internal channels 3bk (in this case k=i=1 to 4, but k could take any value greater than or equal to 2). The first circulator Ca is connected to the first incoming and outgoing optical fibers F1a and F2a, while the second circulator Cb is connected to the second incoming and outgoing optical fibers F1b and F2b. Furthermore, the internal channels 3ai and 3bk are respectively connected to send and receive modules Ma and Mb.
By means of this configuration, it is possible to extract optical resources coming from the incoming optical fiber F1a (or F1b) either to feed at least one of the receive modules Ri (or Rk) after being demultiplexed by the internal channel 3ai (or 3bk) of the OMAD 2, or else to be reinserted into the outgoing optical fiber F2a (or F2b) after being reflected and possibly attenuated. Furthermore, it is possible to insert optical resources coming from at least one of the send modules Ti (or Tk) into the outgoing optical fiber F2a (or F2b), possibly after attenuation.
It is also possible to envisage transferring optical resources from one of the optical fibers to the other optical fiber by establishing connections between the send and receive modules Mai and Mbk. Such a situation is shown in
More precisely, this configuration consists in sending a signal coming from a port (or internal channel) 3ai (or 3bk) to a port 3bk (or 3ai). For this purpose, and for flexibility purposes, it is possible to use 2×2 type optical switches 17 and 18, for example.
The switch 17 has a first inlet/outlet connected to the secondary inlet/outlet ES2 of the first internal channel 3a-1, a second inlet/outlet connected to the first send and receive module M1 (T1, R1), a third inlet/outlet connected to the secondary inlet/outlet ES2 of the first internal channel 3b-1, and a fourth inlet/outlet connected to the fifth send and receive module M5 (T5, R5). Similarly, the switch 18 comprises a first inlet/outlet connected to the secondary inlet/outlet ES2 of the fourth internal channel 3a-4, a second inlet/outlet connected to the fourth send and receive module M4 (T4, R4), a third inlet/outlet connected to the secondary inlet/outlet ES2 of the fourth internal channel 3b-4, and a fourth inlet/outlet connected to the eighth send and receive module M8 (T8, R8).
By configuring the switch 17 as shown in the left-hand portion of
Numerous other combinations can be envisaged. Thus, for example, it is possible to connect the ports of the send modules Ti and the receive modules Ri directly to the corresponding secondary inlets/outlets ES2i in order to redirect a channel. Furthermore, in the example shown in
The invention provides an optical multiplexer device for inserting/dropping optical resources that is compact, of low cost, easy to integrate (because it can be implemented using planar technology), and presenting low insertion losses (since it does not require a coupler upstream from its demultiplexer means).
The invention is not limited to the embodiments of the optical device and the network equipment as described above, merely by way of example, but covers any variant that could be envisaged by the person skilled in the art within the ambit of the following claims.
Number | Date | Country | Kind |
---|---|---|---|
03 14 120 | Dec 2003 | FR | national |