Methods and devices for IQ time skew and conjugation compensation and calibration of a coherent transmitter or transceiver are described. A pilot tone is combined with a digital data signal such that relative powers of the pilot tone in each of two frequency bands of the transmitted data signal may be detected by a pilot tone detector and used to calculate the time skew between I and Q modulation channels of the transmitter. A transmitter DSP applies IQ time skew bias to the data signal to compensate for any calculated IQ time skew. The pilot tone detector also provides the transmitter DSP with the information necessary to detect phase conjugation of the optical signal, which can be corrected by inverting the polarity of the data signal or changing the phase bias point of the optical modulator.

The present application provides a method for transmitting performance parameters of a far-end optical module of a far-end node, a detection method for detecting performance of a far-end optical module, a method for transmitting control parameters for controlling a far-end optical module of a far-end node, a method for controlling a far-end optical module of a far-end node, a far-end optical module, a near-end optical module, and a fronthaul system. The method for transmitting performance parameters includes: generating, in response to at least one of a plurality of registers of the far-end optical module becoming a first source register, an uplink optical signal according to ID information and a register value of the first source register, where the first source register is a register having a changed register value of the plurality of registers, and register values of the registers have a mapping relationship with performance parameters of the far-end optical module; and transmitting the uplink optical signal to a near-end optical module of a near-end node.

An optical network component, system, and method are herein described. The system and method include introducing an AM tone and data to an optical modulator generating a modulated optical signal, measuring an amplitude response of the AM tone within the modulated optical signal, calculating a frequency response based on the amplitude response, and calibrating the optical modulator with the frequency response.

The disclosure is directed at a method and system for optical telecommunications performance monitoring via a dual frequency pilot tone. By applying a dual frequency pilot tone, with a first pilot tone frequency selected from a low frequency band and a second pilot tone frequency selected from a high frequency band, either simultaneously or alternatively, to a wavelength channel, one of the pilot tone frequencies may be adaptively selected to improve wavelength channel monitoring. More specifically, stimulated Raman scattering (SRS) caused crosstalk and chromatic dispersion (CD) caused pilot fading which adversely affect performance monitoring of the wavelength channel may be reduced.

An aspect of the disclosure provides methods and systems for encoding a data bit stream onto a pilot tone signal. Another aspect of the disclosure provides method and systems for pilot tone detection. In both, a coded pilot tone signal is encoded using a code sequence m.sub.1 for each bit value of 1 (b.sub.1) and a code sequence m.sub.0 for each bit value of 0 (b.sub.0) of a data bit stream including pilot tone data bit values of 1 (b.sub.1) and bit values of 0 (b.sub.0), with each code sequence having multiple coding bits in the duration of each bit. Pilot tone detection can further include decoding each code sequence of the coded pilot tone signal using a plurality of successive overlapping measurement windows. In some embodiments each measurement window is of the same duration, being of the duration of each code sequence, and detecting each code sequence comprises selecting one of the plurality of measurement windows to represent a complete code sequence.

A reception apparatus includes: a receiving unit configured to coherently detect an optical signal and output an electrical signal containing a modulated signal and a pilot signal; a first compensating unit configured to detect a frequency of the pilot signal by performing a DFT of the electrical signal, and determine and compensate for frequency error in the electrical signal based on a reference frequency; a frequency converting unit configured to convert the frequency of the pilot signal after the compensating such that the frequency of the pilot signal is lowered by the reference frequency; and a second compensating unit configured to determine frequency error in the modulated signal after the compensating by performing a DFT on the pilot signal after the frequency converting and detecting a frequency of the pilot signal after the frequency converting.

A probe generator includes: a first demultiplexer configured to branch a first optical signal having a first wavelength into at least two first polarized optical signals; a first adjustor configured to adjust the first polarized optical signals such that the first polarized optical signals have the same polarization direction and to combine the adjusted first polarized optical signals into a second optical signal; a first modulator configured to branch the second optical signal into at least two first split optical signals and to intensity-modulate each of the first split optical signals with first pilot signals; a second adjustor configured to adjust the first split optical signals intensity-modulated by the first modulator such that the intensity-modulated first split optical signals have different polarization directions; and an output unit configured to combine the first split optical signals adjusted by the second adjustor to generate a probe optical signal to be output.

The disclosure is directed to a method and system for generating a pilot tone for an optical signal with an optical telecommunications system. The pilot tone is generated in the digital domain by modulating the data to be transmitted to a destination node within the optical telecommunications network. The modulation of the data introduces occurrence modulation to the optical signal.

The invention relates to a method for creating a control channel in an optical transmission signal, wherein the optical transmission signal (S.sub.DS,i, S.sub.US,i) includes an optical carrier frequency component, a higher frequency modulation component carrying user information to be transported from a first end to a second end of an optical transmission link and a lower frequency modulation component carrying control information, the higher frequency modulation component realizing a user channel and the lower frequency modulation component realizing the control channel, and wherein the lower frequency modulation component is created by amplitude modulation. According to the invention, the lower frequency modulation component includes a binary digital pilot tone signal component which corresponds to a pilot tone signal having a predetermined pilot tone frequency (f.sub.i).

In an asynchronous optical modulation system, a drive circuit may generate a plurality of dither tones in accordance with a predetermined dither frequency ratio. Based on the components of the dither frequency ratio, the optical modulation system may be configured to determine a feedback signal magnitude component that is independent of the delay τ and a feedback signal sign component that is also independent of the delay τ. A feedback signal that is independent of the delay τ can then be reconstructed based on the feedback signal magnitude component and the feedback signal sign component.