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.

An optical transmission device includes: a selector configured to select a wavelength of a signal to be transmitted to an optical transmission line and output a wavelength-multiplexed signal; an adjustor configured to control a power level of the wavelength-multiplexed signal; and a controller configured to control the adjustor or the selector, wherein the selector selects a wavelength of an optical signal in a second wavelength band different from an existing first wavelength band, and when the second wavelength band is added to or removed from the optical transmission line, the controller controls power of the wavelength-multiplexed signal in the second wavelength band at a slower speed than power control in the first wavelength band.

A detection system for monitoring the intensity of a stream of modulated pulses, the system comprising a controller configured to provide a control signal to a component outputting modulated pulses the control signal controlling the level of modulation for each pulse exiting the component and a detector configured to measure the intensity of the pulses in the stream of pulses exiting the component outputting modulated pulses, wherein the detector comprises a gated detector, the controller being configured to send a gating signal to said detector, wherein said gating signal varies the gain of the detector with the control signal, such that pulses with a selected modulation level can be detected.

A communication device is provided that estimates one or more disturbance values associated with one or more components of the communication device, and adjusts the communication device to change a received power of the output signal. The communication device includes a transmitter having a seed laser configured to provide an amount of bandwidth for an output signal, an Erbium-doped fiber amplifier (EDFA) configured to increase an amplitude of the output signal, and a single mode variable optical attenuator (SMVOA) configured to decrease the amplitude of the output signal.

A tap photodetector includes at least one detection unit configured to detect an optical signal. Each detection unit may separately detect an optical signal. Each detection unit includes a transparent zone and a detection zone. The transparent zone is configured to transmit a part of an optical signal, and the detection zone is disposed on a periphery of the transparent zone and is configured to detect another part of the optical signal that does not pass through the transparent zone.

A method and an apparatus for digitally and automatically controlling a bias voltage of an electro-optic optical modulator are disclosed. The method includes: outputting a scanning bias voltage; acquiring a first optical signal; converting the first optical signal into a first electrical signal; outputting a first direct current signal; calculating an operating bias voltage at each operating point and a half-wave voltage; calculating an error feedback coefficient and a dither amplitude; outputting an operating bias voltage and a dither signal with the dither amplitude; acquiring a second optical signal; converting the second optical signal into a second electrical signal; outputting a harmonic component; calculating a harmonic amplitude and a shift phase; calculating a new bias voltage; and using the new bias voltage as the operating bias voltage.

A method for calculating configuration of an optical transmission network includes: acquiring an initial value of an input power of an optical cable; based on the initial value, obtaining an output power of each channel at an end of a section of the optical cable according to a loss of the optical cable; taking the output power of each channel at the end of the section as a boundary condition to calculate the input power of each channel at the section based on an amount of optical power transferred from a high-frequency channel to a low-frequency channel due to an SRS effect; and calculating a first parameter value of an optical amplifier of the section using the input power of each channel at the section and the output power of each channel at the end of a preceding section of the section.

Embodiments of the present invention relate to method and device for measuring optical signal-to-noise ratio (OSNR). A method for measuring an OSNR of a signal of interest may comprise: obtaining spectrum of the signal of interest, the spectrum including power spectrum density distribution of the signal of interest in a channel bandwidth B; obtaining spectrum of a comparative signal that has the same spectrum characteristics as but different OSNR than the signal of interest, the spectrum including power spectrum density distribution of the comparative signal in the channel bandwidth B; and calculating the OSNR of the signal of interest by using the spectrum of the signal of interest and the spectrum of a comparative signal.

An optical network unit (ONU) comprising a media access controller (MAC) configured to support biasing a laser transmitter to compensate for temperature related wavelength drift receiving a transmission timing instruction from an optical network control node, obtaining transmission power information for the laser transmitter, estimating a burst mode time period for the laser transmitter according to the transmission timing instruction, and calculating a laser phase fine tuning compensation value for the laser transmitter according to the burst mode time period and the transmission power information, and forwarding the laser phase fine tuning compensation value toward a bias controller to support biasing a phase of the laser transmitter.

A loss-based wavelength meter includes a first photodiode configured to measure power of monochromatic light; and a loss section having a monotonic wavelength dependency, wherein a wavelength of the monochromatic light is determined based on measurements of the first photodiode after the monochromatic light has gone through the loss section. This provides a compact implementation that may be used in integrated optics devices using silicon photonics as well as other embodiments.