Abstract: Apparatus for processing an optical signal carrying symbols. Modulation conversion means converts the optical signal from a first format, wherein each symbol has a unique nominal phase, to a second format, wherein each symbol has a unique combination of nominal phase and nominal amplitude. The modulation conversion means includes a signal splitter for splitting the optical input signal into two optical partial signals, which are directed to respective optical paths. Delay elements cause a mutual temporal difference between the two optical partial signals, which are processed in at least one non-linear regenerator having at least two ports and a gain which depends on the combined signal power directed to the at least two ports. The apparatus directs the optical partial signals from the modulation conversion means to an internal or external photo detector stage in the second format.

Abstract: A device for processing of an optical input signal includes at least a first data signal. A first optical resonator provides a reference signal by optical filtering of the optical input signal. The first optical resonator is matched with a predetermined reference wavelength of the first data signal. A second optical resonator provides a sideband signal by optical filtering of the optical input signal. The second optical resonator is non-matched with the predetermined reference wavelength of the first data signal. An optical combiner combines the sideband signal with the reference signal to form an optical output signal.

Abstract: Simultaneous recovery of several different clock signals is based on coupling an optical input signal into an optical resonator matched with at least four spectral peaks of the input signal. The input signal having arbitrary polarization is divided by a polarizing splitter into a first signal having horizontal polarization and a second signal having vertical polarization. The polarization of the first signal is rotated 90 degrees such that the polarization of the first signal is parallel to the vertical polarization second signal. Both vertically polarized signals are passed through the same optical resonator in opposite directions, and they are combined after passing through the resonator in order to form an output signal. The spectral separation between the first peak and the second peak is equal to a first clock frequency, and the spectral separation between the third peak and the fourth peak is equal to a second clock frequency.

Abstract: The invention relates to clock recovery in optical communication systems. Optical clock frequencies are recovered from a plurality of optical channels by using a single optical resonator. The optical resonator is matched with the carrier frequencies and the sideband frequencies of the data signals sent at different channels. The separation range of the optical resonator is selected such that the clock frequency of at least one data signal is substantially equal to the separation range of the optical resonator multiplied by an integer greater than or equal to two. The method according to the invention allows the use of different clock frequencies at different optical channels. Furthermore, the method provides considerable freedom to select the spectral positions of the optical channels.

Abstract: A clock recovery device adapted to recover at least one clock signal from an optical input signal. The input signal includes at least one data signal. The clock recovery device-includes a first waveguide, a first optical resonator coupled to the first waveguide, a second optical resonator coupled to the first waveguide, and a combiner to combine signals provided by the first optical resonator and the second optical resonator in order to provide an output signal. A passband of the first optical resonator is matched with a first spectral peak of the input signal, and a passband of the second optical resonator is matched with a second spectral peak of the input signal such that the spectral separation between the first and the second peaks is equal to a clock frequency associated with a first data signal. The optical resonators store optical energy and provide an output also when the data signal is zero.