T 1547/08 – With A Little Help From My Friends

Although Boards have to be strictly impartial in inter partes proceedings, they may sometimes provide some help to parties in ex parte proceedings. This appears to have happened in the present case where an applicant filed an appeal against the decision of the Examining Division (ED) to refuse its application because the invention was insufficiently disclosed.

Claim 1 on file before the Board read:

A device (12) for regenerating the phase of an optical signal (Se) carrying an information encoded by modulating the phase of said signal, the device comprising:
an optical modulation converter (14;42) for converting the signal carrying the information encoded by phase modulation into at least one secondary signal (S’1, S’2) carrying said information encoded by amplitude modulation;
at least one optical amplitude regeneration module (16;44) for regenerating the amplitude of the secondary signal; and
an optical modulation converter (18;14;42) for converting the regenerated secondary signal into a signal (Ss) carrying the information encoded by phase modulation.

There was a telephone interview with the rapporteur of the Board (again something that is not likely in inter partes proceedings, see T 263/07), who, inter alia, drew the applicant’s attention to documents A1 and A2, which appeared to confirm its arguments in support of sufficiency of disclosure.

*** Translated from the French ***

[2.2] In its decision the ED, although it did not cast doubt on the fact that the technical means disclosed in the application were sufficient for carrying out the [steps of converting the signal carrying the information into a secondary signal, regenerating the amplitude of the secondary signal and concerting the regenerated secondary signal into the signal Ss] individually, considered that neither the sequence of steps mentioned nor the assembly of technical means carrying out the different steps were capable of obtaining the claimed effect, i.e. regenerating the phase of an optical signal carrying an information encoded by modulating the phase. In particular, the ED pointed out that the embodiments proposed in the description did not allow to suppress, even partially, the phase noise of the optical signal, for the following reasons:

as there was noise in the original signal Se, each of both complementary intermediary signals S’1 and S’2 contain amplitude noise and also a phase noise having a spectral density corresponding to the spectral density of the original signal;

the amplitude regeneration module, which was implemented e.g. as an saturable absorber, only had the role of suppressing the intermediary signal having an amplitude close to zero – thus the complementary intermediary signal having a high amplitude would be transmitted without phase modification; and

therefore, the regeneration module allowed to regenerate the amplitude but this amplitude regeneration had no effect on the phase of the optical signals and the output signal Ss would still carry the phase noise of the original signal.

[2.3] The applicant submitted that the device suppressed the phase noise stemming from the low levels (issu des niveaux bas) of the output signal by neutralizing the power of the intermediate signals at low levels (sur les niveaux bas) by eliminating their fluctuation amplitude close to the low levels.

Having studied the questions raised by the ED and the arguments submitted by the [applicant], the Board considers that even though the doubts expressed by the ED are not unfounded on a technical level, the arguments presented by the [applicant] make it credible that the claimed effect can indeed be obtained, at least (as stated in the application […]) to a certain degree.

As a matter of fact, it is undisputed that the low amplitude component of the intermediary signals issued by the first optical modulation converter is eliminated by the amplitude regeneration module. As this eliminated component itself carries phase noise stemming from the phase noise of the original signal and as the signal that is reconstructed from the high power component and issued by the second modulation converter does not contain any contribution of the eliminated component, the Board is of the opinion that one may expect that the reconstructed signal carries phase noise that is reduced with respect to the phase noise of the same signal that is reconstructed without suppressing said intermediary low amplitude component, as can be seen from the constellation diagrams of the intermediary signals on the input and the output of the regeneration module that are shown in the statement of grounds of appeal. Moreover, as pointed out by the [applicant] in its argumentation, any action of the amplitude regeneration module on the amplitude fluctuations of the high power component could only amplify or at least maintain the mentioned effect.

Incidentally, this conclusion is confirmed by the documents known to the Board and brought to the attention of the [applicant], i.e. documents A1 and A2. Each of these documents discloses a device for treating a modulated signal of the DPSK (“differential phase-shift keying”) type, which is the type considered in the application […], the devices being of the same type as the claimed device and using saturable absorbers of the type used in the embodiments disclosed in the application […]. These documents show in detail that the phase nose of the signal issued by the devices is partially eliminated […]. They have been published after the filing date of the application but nevertheless constitute proof (see e.g. decision T 1264/04 [5-7]) for the [applicant’s] assertions according to which the means disclosed in the application and available at the date of filing of the application are capable of reducing or partially eliminating the phase noise of the optical signal encoded by phase modulation.

Thus the device that is claimed and disclosed in the application allows to obtain the claimed effect of regenerating, at least to some extent, the phase of an optical signal carrying information encoded by modulating the phase of the signal.

[2.4] On the basis of what has been said, the Board comes to the conclusion that the reasons given by the ED for refusing the application are not convincing and that the application discloses the claimed invention in a manner sufficiently clear and complete for it to be carried out on the filing date by a person skilled in the art, as required by A 83.

Should you wish to read the whole decision (in French), please click here.

The file wrapper can be found here.