the general principle of the invention is described with reference to fig2 which shows a set of optical fiber cables 200 in which the propagation direction of each individual fiber , for example the fiber 210 , is not allocated in a fixed manner , in contradistinction to the prior art previously discussed with reference to fig1 a to 1 c . the optical fibers must access a device 230 consisting of a plurality of subdevices d 1 , d 2 , d 3 for processing optical signals that they transport . these devices include devices of the type shown in fig1 a to 1 c , i . e . oxc , oadm and optical amplifiers . of course , the above list is not limiting on the invention and refers only to standard optical devices to which the invention may be relevant . according to the invention , access to these devices is obtained via an n × n optical switch 260 which is capable of optically connecting any of n upper inputs / outputs 270 and any n lower inputs / outputs 210 . in this instance , n corresponds to the total number of inputs and outputs of the optical device 230 , of which there are 16 in this particular example , divided into seven outputs 240 and nine inputs 250 connected to the upper inputs / outputs 270 of the optical switch 260 . various kinds of optical device 230 are available for processing information circulating on all the cables 200 and thus on at least n fibers , 16 fibers in this example being connected to the lower inputs / outputs 210 of the optical switch . accordingly , the optical fibers can be distributed individually to make best use of the optical devices as a function of the traffic to be transported at a given time . this implies that the direction of circulation of the light signals 115 in the optical switch 260 is interchangeable between the top inputs / outputs 270 and the bottom inputs / outputs 210 . fig2 is merely one particular example of the use of the optical switch 260 , of course . based on the fig2 general solution , fig3 shows a more specific embodiment of the invention using smaller optical switches which therefore do not individually have the necessary 2 × n inputs / outputs . the switch 260 in fig2 can therefore be implemented in practice using two groups of smaller switches , for example . a first group comprises four 4 × 9 switches 224 constituting a first switching layer feeding a second layer comprising 4 × 2 switches 228 and 4 × 1 switches 227 ( the 4 × 1 switches can in practice be 4 × 2 switches of which only one output is used ). this provides the same functionality as fig2 but with small switches . it will be noted in particular that the first layer of switches associates a switch with each cable , thus authorizing the switching of any fiber of a cable to any switch of the second layer . the latter associates a switch with each input / output pair of the directional device 230 . if there are more inputs than outputs , as is the case in the fig3 example , in which there are nine inputs and seven outputs , the second layer must further associate a switch 227 with each supplementary input , of which there are two in this example . the converse is equally true . if the directional device 230 has more outputs than inputs , a switch must be associated with each supplementary output . accordingly , each of these switches of the second layer can connect an input and an output separately to two separate cables via the switches of the first layer . the invention can be implemented in various ways without in any way departing from the spirit of the invention . in particular , simplifications can be made as a function of the optical devices that are accessed by the optical fibers . fig4 a shows a series of optical add and drop multiplexers ( oadm ) 300 , 310 and 320 such as might be found in the successive nodes of a ring network , for example . in this case , as the loop comprises cables with four fibers 330 , one 4 × 4 optical switch 340 is sufficient , with the four 2 × 2 switches 350 , to rearrange the circulation direction of the fibers , whereas an 8 × 8 switch was necessary in the fig2 general case and two 4 × 4 switches were necessary in fig3 . fig4 a is merely one example of the arrangements possible with this configuration , in which the optical devices are oadm or similar devices , in which example each 2 × 2 switch is connected on one side directly to an input and to an output of the optical devices 300 , 310 , 320 and on the other side to each of the two cables , directly in the case of one of them and via a 4 × 4 switching matrix 340 in the case of the other one . [ 0025 ] fig4 b and 4c show other possible arrangements using the same result in terms of the number of elements necessary . fig4 b shows the example of an 8 × 8 switch 360 placed in front of the eight inputs of an optical device 370 of the fig4 a type while two cables each with eight fibers are connected to eight 2 × 2 optical switches similar to those of fig4 a . if this particular embodiment is compared to the general solution described with reference to fig2 it will immediately be noted that a 16 × 16 switch would normally have had to be used . the embodiment shown in fig4 b can also be compared to that described with reference to fig3 and which would have required the use of two 8 × 8 switches , whereas only one is necessary here . also , it will be noted that , compared to fig4 a , it is merely a question of a different position of the switch 360 . whereas in fig4 a the switch 340 is placed in front of the 2 × 2 switches 350 , in fig4 b it is placed between the 2 × 2 switches and the optical devices 370 . [ 0026 ] fig4 c shows another position for the 8 × 8 switch 360 from the previous figure , the switch here being placed at the output of the optical devices 370 . [ 0027 ] fig5 shows another embodiment of the invention which achieves even greater simplification in the case of optical amplifier type devices 400 . in this case , the ports are divided between two cables and only 2 × 2 optical switches 410 are necessary to be able to use the fibers and the amplifiers in either direction . also , each of the 2 × 2 switches is connected directly to an input and an output of the amplifier . [ 0028 ] fig3 fig4 a , 4b and 4 c , and fig5 are intended to show that the invention can be implemented in many forms with particular advantages as a function of the optical devices used and the optical fiber cable configurations to be interconnected . the person skilled in the art will understand the advantages of using , in a particular context , one or the other of those forms of the invention .