A method for generating a tone signal (TS) having a tone frequency, f, wherein the method comprises the following steps: supplying (S1) a binary bit stream (BBS) having a mark pattern with a supply bit rate, BR, to a signal filter unit; and filtering (S2) the supplied binary bit stream (BBS) by said signal filter unit to generate the tone signal (TS), wherein the mark pattern of the binary bit stream (BBS) supplied to said signal filter unit is adapted to minimize a ratio of the supply bit rate, BR, to the tone frequency, f, of the generated tone signal (TS).

A light modulation element constituted by a substrate type optical waveguide has a Mach-Zehnder interferometer; and a traveling wave electrode having a signal electrode arranged at least between a first phase modulator and a second phase modulator and electrically connected to both of the first phase modulator and the second phase modulator. A polarity of a semiconductor region of the first phase modulator connected to the signal electrode and a plurality of a semiconductor region of the second phase modulator connected to the signal electrode are different from each other.

An optical waveguide modulator with automatic bias control is disclosed. A portion of the modulator light is mixed with reference light and converted to one or more electrical feedback signals. An electrical feedback circuit controls the modulator bias responsive to the feedback signals.

The present invention discloses an optical module and a detection circuit thereof. The detection circuit includes: a sampling module, including a first potentiometer configured to convert a sampling current into a sampling voltage; an amplifying module, coupled to an output end of the sampling module and configured to amplify the sampling voltage; and an analog-to-digital conversion module, coupled to an output end of the amplifying module and configured to convert the amplified sampling voltage into a digital signal for detection. By arranging a potentiometer in a sampling module of a detection circuit, a resistance value of the sampling module can be adjusted, thereby adapting to responsivities of different modulators, increasing the locking speed of a modulator, preventing horizontal shifts of a locking point and a false locking point, and reducing the occupied PCB area.

Systems and methods described herein include methods and systems for controlling bias voltage provided to an optical modulating device. The optical modulating device is biased at a bias point that is different from a null point of the device such that an offset to the received optical power due to limited extinction ratio is reduced.

An optical transmission device includes an optical modulator and a processor. The optical modulator optically modulates an optical signal with a driving signal to output a modulated optical signal. The processor performs ABC on a bias of the optical modulator, using the modulated optical signal, so as to cause the bias to converge to an optimum point. The processor starts the ABC using a modulated optical signal optically modulated with a QPSK signal at start-up timing, acquires an optimum value that is a bias value when the bias converges to the optimum point, and stops the ABC. After the ABC is stopped, the processor sets the acquired optimum value as an initial value, and restarts the ABC using a modulated optical signal optically modulated with an N-QPSK signal.

The present disclosure discloses a method and an apparatus for automatically controlling a bias voltage of an optical modulator. The method includes: calculating a new Q bias voltage based on an acquired Q reference phase, a Q harmonic phase, a Q harmonic amplitude, a Q bias voltage and a Q error feedback coefficient, calculating a new I bias voltage based on an I reference phase, an I harmonic phase, an I harmonic amplitude, an I bias voltage and an I error feedback coefficient, and calculating a new P bias voltage based on a P reference phase, a P harmonic phase, a P harmonic amplitude, a P bias voltage and a P error feedback coefficient.

An optical transmitter has an array of laser diodes, which output optical signals from a forward end, and controls the power of the optical signals. The optical transmitter has photodiodes detecting the optical power of optical signals from a reverse end and a LD-DRV unit that supplies to the laser diodes, bias current amplitude modulated to a predetermined frequency that differs from that of the drive signal of the laser diodes. The optical transmitter has a frequency analyzing unit that separates a signal detected by a photodiode, into an optical signal component from a target laser diode and crosstalk optical signal components received from other laser diodes; and a control unit that computes for each detected signal, a ratio of the crosstalk optical signal components to the optical signal component, and performs based on the ratio, a computation to remove the crosstalk optical signal components from the detected signal.

A method/system described herein addresses the intrinsic nonlinearity of electrooptic modulators and the restrictions placed on the signals dynamic range in applications such as data communication and sensing. Linear electro-optic modulation utilizing ring resonator electrooptic modulators is produced over a dramatically wider range of the input signal amplitude, which improves the dynamic range and the amount of information that is transmitted via laser light. A distributed and subranging design folds the large dynamic range across multiple linear subranges, with each subrange being addressed using a unique optical wavelength, or a unique optical fiber, or a unique free space path. The subrange within the wide dynamic range of the input signal is captured by the linear portion of the transfer function of a single transfer function. This enables the efficient use of optical links for the transmission and processing of analog and multilevel signals, overcoming the limitations that were hindering progress.

An optical module includes: an optical modulator, a superimposing unit, an offset adding unit, a detector, and a bias controller. The optical modulator includes a first modulator to generate a first optical signal, a second modulator to generate a second optical signal and a phase shifter to provide a specified phase difference between the first optical signal and the second optical signal so as to generate a modulated optical signal. The superimposing unit superimposes a low frequency signal on a DC bias of the first modulator. The offset adding unit adds an offset to a DC bias of the second modulator. The detector detects a low frequency component from output light of the optical modulator. The bias controller controls a DC bias that is applied to the phase shifter based on the low frequency component detected by the detector.