Abstract: An optical transmitter includes: a controller that generates a multi-level amplitude modulated signal based on transmission data that is binary data; a driver that generates a drive signal in accordance with the multi-level amplitude modulated signal; and a light emitter that generates an optical signal in accordance with the drive signal. The controller selects one of a first encoding method and a second encoding method in accordance with a switching signal. The controller generates the multi-level amplitude modulated signal by converting a bit string of M (M is an integer of 2 or more) bits included in the transmission data into a pulse signal having 2M logic levels using a selected encoding method. The controller sets voltage values of the 2M logic levels depending on the selected encoding method.

Abstract: Provided is an optical submodule which includes an optical transmission/reception module that optically couples an optical transmission signal and an optical reception signal into one optical fiber and a flexible printed circuit board (FPCB) mounted on the optical transmission/reception module that functions as an electrical signal interface with a main board, and an electrical signal line of an optical transmission channel for the optical transmission signal and an electrical signal line of an optical reception channel for the optical reception signal may be deployed on different sides of the FPCB.

Abstract: Ethernet link extension methods and devices provide, in one illustrative embodiment, an Ethernet link extender with physical medium attachment (PMA) circuits each having a transmitter and receiver that communicate with a respective node in a sequence of communication phases. The sequence includes at least an auto-negotiation phase and a subsequent training phase, the phases occurring simultaneously for both PMA circuits. In the auto-negotiation phase, the PMA circuits operate in a pass-through mode, rendering the extender transparent to the two nodes. In the training phase, the PMA circuits operate independently, sending training frames to their respective nodes based in part on received back-channel information and locally-determined training status information. The training phases may be prolonged if needed to provide a simultaneous transition to a frame-forwarding phase of the sequence.

Abstract: An optical receiver includes an optical filter that transmits signal light to be received from wavelength-multiplexed signal light, a light source that outputs local oscillation light, a 90-degree hybrid circuit that causes the local oscillation light output from the light source to interfere with the signal light transmitted through the optical filter to output interference signal light, a converter that converts the interference signal light into an electrical data signal, a spectrum detector that detects a frequency spectrum of the electrical data signal based on the electrical data signal, and a controller that controls a center frequency of a passband of the optical filter based on a shape of the frequency spectrum.

Abstract: A electronic method, includes receiving, by a graphene structure, a SPP mode of a particular frequency. The electronic method includes receiving, by the graphene structure, a driving microwave voltage. The electronic method includes generating, by the graphene structure, an entanglement between optical and voltage fields.

Abstract: The invention provides a method for nonlinear compensation of coherent high-capacity high-order QAM system, including: deploying an OPC on an intermediate link of communication between a transmitter and receiver, and performing phase conjugation on a transmitted signal based on the OPC to generate idler; performing phase recovery on a compensated signal at the receiver to obtain a constellation diagram, simulating a nonlinear function relationship between a transmitted signal and a received signal by using a trained and learned CVDNN, and performing nonlinear compensation on the constellation diagram to obtain the compensated constellation diagram; and calculating a Q-factor based on the compensated constellation diagram, and evaluating communication performance by the Q-factor. Nonlinear compensation is performed on a transmitted signal by using an OPC+CVDNN method to equalize nonlinear degradation of an optical fiber in a WDM coherent optical communication system.

Abstract: An optical positioning-navigation-timing (PNT) system includes a managed optical communications array (MOCA) transceiver. The MOCA transceiver includes an array of optical transceivers for transmitting and receiving optical signals, each optical transceiver including a laser and a beam steering element, and a controller for controlling the operation of the array of optical transceivers. Each optical transceiver is adjustable for optical parameters of the optical signals so transmitted and received, the optical parameters including at least one of phase, angle, wavelength, time delay, amplitude, pulse delay, polarization, timing offset, phase, and divergence angle. Further, the controller is configured for controlling the optical parameters to include PNT data in a portion of the optical signal transmitted from the MOCA transceiver.

Abstract: Provided is a light detecting device including a light input device configured to receive light, a plurality of waveguides extending from the light input device, the plurality of waveguides being configured to transmit portions of the light received by the light input device, respectively, a plurality of modulators provided on the plurality of waveguides and configured to modulate phases of the portions of light transmitted in the plurality of waveguides, respectively, at least one graphene layer configured to absorb the portions of light transmitted in the plurality of waveguides, and at least one first electrode and at least one second electrode electrically connected to the at least one graphene layer, respectively.

Abstract: This invention pertains to the field of free-space optical (FSO) communications, and specifically to the realization of functional FSO optical transceiver terminals located at remote electrically unpowered locations within a communications network. A remote unpowered FSO terminal located at a far-end location receives necessary optical power from a powered base station location (near-end) required for all optical amplification functions necessary for NRZ or RZ format signals within the spectral range of 900 nm to 1480 nm as well as an Ultra Short Pulsed Laser (USPL) centered at 1560 nm at the far-end location. A transmitting node identified as the near-end transmits an optical signal identified as a pump signal to a remote location classified as the far-end node over a free space medium, such as the atmosphere, where the far-end node location does not have available electrical power for operation of electro-optic components required for transmission and retransmission functions.

Abstract: A circuit board (100) has a first surface (102). A semiconductor chip (200) (first semiconductor chip) is located at the first surface side (102) of the circuit board (100). An insulating layer (300) covers the first surface (102) of the circuit board (100) and the semiconductor chip (200). A conductive path (310) (first conductive path) is electrically connected to the semiconductor chip (200) and extends in the insulating layer (300). A waveguide (320) is optically coupled to the semiconductor chip (200) and extends in the insulating layer (300).

Abstract: A data storage device and method for real-time data locking in surveillance storage are provided. In one embodiment, a data storage device is provided comprising a memory and a controller. The controller is configured to receive an image of an object of interest from a host; receive a video stream from the host; and as the video stream is being received from the host, determine whether the object of interest is present in the video stream. Other embodiments are provided.

Abstract: A semiconductor package includes an upper substrate having a first surface and a second surface which are opposite to each other, a lower semiconductor chip disposed on the first surface of the upper substrate, a plurality of conductive pillars disposed on the first surface of the upper substrate at at least one side of the lower semiconductor chip, and an upper semiconductor chip disposed on the second surface of the upper substrate. The lower semiconductor chip and the plurality of conductive pillars are connected to the first surface of the upper substrate, and the upper semiconductor chip is connected to the second surface of the upper substrate.

Abstract: Systems, devices, methods, and computer readable medium for transmitting data using polynomials and instantaneous spectral analysis. In and/or prior to the transmitter, a signal may be formed by fitting the data with a Taylor series polynomial, which is projected onto Cairns series functions. The Cairns series functions are converted into Cairns exponential functions, which are combined based on frequency information to produce the set of sinusoidals with continuously time-varying amplitude, each of the sinusoidals having a different frequency.

Abstract: According to one general aspect, an apparatus may include a memory circuit die configured to store a lookup table that converts first data to second data. The apparatus may also include a logic circuit die comprising combinatorial logic circuits configured to receive the second data. The apparatus may further include an optical via coupled between the memory circuit die and the logical circuit die and configured to transfer second data between the memory circuit die and the logic circuit die.

Abstract: A symbol-determining device according to an embodiment includes: a transmission line shortening unit that multiplies each symbol value of a symbol array that is part of an input signal by a tap gain of a linear digital filter and outputs a symbol array representing a sum of values acquired through the multiplication; a transmission line estimating unit that estimates a transfer function of a transmission line using an adaptive nonlinear digital filter on the basis of a symbol array representing a state of the transmission line; an addition comparison processing unit that calculates a minimum value of a distance function in a Viterbi algorithm on the basis of a metric that is calculated on the basis of the output of the transmission line shortening unit and the transfer function; and a path tracing-back determination unit that performs symbol determination by tracing back a trellis path in the Viterbi algorithm on the basis of the minimum value of the distance function.

Abstract: A laser device includes a laser oscillator that generates a laser beam, condenser lens that condenses laser beam emitted from the laser oscillator, transmission fiber that includes at least core that transmits laser beam condensed by condenser lens, and cladding provided around core, and a lens driving unit that adjusts a position of condenser lens. The lens driving unit automatically adjusts the position of condenser lens to reduce light intensity of laser beam incident on cladding.

Abstract: The present invention facilitates optical modulation skew adjustment. Components of an on chip optical device driver system can cooperatively operate to provide modulated driver signals to drive configuration of optical signals. A serializer is configured to receive parallel data signals and forward corresponding serial data signals. A multiplexing component is configured to selectively output an in-phase component and a quadrature component of the serial data signals, including implementing skew adjustments to aspects of a first output signal and a second output signal. An output stage is configured to output signals that modulate an optical signal, including the first output signal and the second output signal. An on chip skew detector is configured to detect a skew difference between the first output signal and the second output signal. A skew calibration component is configured to direct skew adjustment between the first output signal and the second output signal.

Abstract: Disclosed is a receiver for receiving an optical signal comprising a plurality of carriers within a predetermined frequency band. The receiver comprises means for sampling and converting each of the carriers into a set of corresponding digital signals, and a digital processing unit for processing said digital signals of said set of digital signals such as to mitigate transmission impairments of the corresponding optical carriers based on corresponding processing parameters. The digital processing unit is configured for determining such processing parameters by carrying out a corresponding parameter derivation procedure based on one of the digital signals of said set of digital signals. The processing unit is configured for sharing thus determined processing parameters for processing of other digital signals among said set of digital signals based on said shared determined processing parameters, or processing parameters derived from said shared determined processing parameters.

Abstract: An optical transmission system includes an optical transmitter, an optical receiver, and a control apparatus. The control apparatus repeatedly performs an adjustment process for adjusting power of an optical signal of a frequency band to be adjusted while switching the frequency band to be adjusted between at least two frequency bands including at least a frequency band where stimulated Raman scattering occurs among frequency bands that are multiplexed in a multiplexed optical signal transmitted by the optical transmission system. In the adjustment process, when power of an optical signal of the frequency band to be adjusted transmitted from the optical transmitter has been changed, the control apparatus determines the power of the optical signal of the frequency band to be adjusted on the basis of a signal quality measured by the optical receiver that has received the optical signal.

Abstract: A semiconductor memory stack connected to a processing unit, and associated methods and systems are disclosed. In some embodiments, the semiconductor memory stack may include one or more memory dies attached to and carried by a memory controller die—e.g., high-bandwidth memory. Further, a processing unit (e.g., a processor) may be attached to the memory controller die without an interposer to provide the shortest possible route for signals traveling between the semiconductor memory stack and the processing unit. In addition, the semiconductor memory stack and the processing unit can be attached to a package substrate without an interposer.

Abstract: At least some aspects of the present disclosure provide for a method. In some examples, the method includes receiving 2-line data in an embedded Universal Serial Bus (eUSB) format. The method further includes encoding the 2-line data into a single signal. The single signal comprises a first symbol corresponding to a first state change of the 2-line data and a second symbol corresponding to a second state change of the 2-line data.

Abstract: A method includes placing a fluid guide forming composition in contact with the optical source and with the optical fiber, injecting a first light in the guide forming composition from the optical source and/or from the optical fiber, to harden a central region of the optical guide, illuminating the guide forming composition with the second light to harden a peripheral region of the optical guide by photopolymerization initiated by the second photoinitiator system. The difference between the first peak wavelength and the second peak wavelength being more than 100 nm.

Abstract: A strain gauge arrangement for an axle counter has a strain sensor element, a carrier and a railway line structure that is to be monitored. At least one part of the carrier is maintained in an elastically deformed state by the structure when the carrier is secured to the structure. The carrier is formed from a first carrier piece and a second carrier piece, which lie opposite one another at a distance from one another. The strain sensor element has one first fixing point fixed to the first carrier piece, and one second fixing point fixed to the second carrier piece, and a middle section mounted between the fixing points which are not fixed to the first or second carrier piece. The strain gauge arrangement is simple to handle and a drop can be reliably detected and a strain state of the strain sensor element can be predetermined more easily.

Abstract: A transmission apparatus includes a video obtainer configured to obtain a video signal, a first converter configured to convert the video signal into an electrical signal complying with a high definition multimedia interface (HDMI (registered trademark)) standard, a second converter configured to convert the video signal into an optical signal, and a signal processor configured to perform at least one of the conversion using the first converter and the conversion using the second converter with respect to the obtained video signal.

Abstract: Disclosed in some examples, are optical devices, systems, and machine-readable mediums that send and receive multiple streams of data across a same optical communication path (e.g., a same fiber optic fiber) with a same wavelength using different light sources transmitting at different power levels—thereby increasing the bandwidth of each optical communication path. Each light source corresponding to each stream transmits at a same frequency and on the same optical communication path using a different power level. The receiver differentiates the data for each stream by applying one or more detection models to the photon counts observed at the receiver to determine likely bit assignments for each stream.

Abstract: Techniques for transmitting an optical signal through optical fiber with an improved cost effective stimulated Brillouin scattering (SBS) suppression include externally modulating a light beam emitted from a light source with a high frequency signal. The light beam is also modulated externally with an RF information-carrying signal. The high frequency signals are at least twice a highest frequency of the RF signal. The high frequency signals modulating the light source can be gain and phase adjusted by the first set of gain and phase control circuit to achieve a targeted spectrum shape. The adjusted high frequency signals then are split, providing a portion of the split signals to modulate the light source and another portion of the split signals to the second set of phase and gain control circuit for adjusting a phase/gain.

Abstract: A photonic monobit analog-to-digital converter (ADC) includes an incoherent optical source, a dual optical modulator, a coupler, a coherent detector, a limiter, and a DSP. The incoherent optical source generates an optical noise signal. The dual optical modulator modulates phase and amplitude of an input complex baseband signal onto an input optical signal to generate an optical modulated signal. The coupler couples the modulated signal with the optical noise signal to generate a dithered optical signal. The coherent detector coherently detects a dithered in-phase (I) signal component and a dithered quadrature (Q) signal component associated with the input complex baseband signal using the dithered optical signal and a reference optical signal. The limiter outputs a complex decision signal based on the dithered I and Q signal components. The DSP generates a digital signal representative of the input complex baseband signal based on the complex decision signal.

Abstract: An embodiment includes an optical transmitter. An optical transmitter may include a primary laser for transmitting a primary optical signal and a backup laser for transmitting a backup optical signal. The optical transmitter may further include a photonic integrated circuit (PIC). The PIC may include at least one input port configured to receive the primary optical signal from the primary laser and the backup optical signal from the backup laser. The PIC may also include at least one output port configured to receive each of the primary optical signal and the backup optical signal. The optical transmitter may be configured to activate the backup laser upon determining that the primary laser has failed or is failing.

Abstract: Embodiments of the present application provide an optical signal generation device. The device includes a laser, a first modulator, a second modulator, a first adjustment module, and a beam combiner. The laser is configured to: output a first optical signal to the first modulator, and output a second optical signal to the second modulator. The two modulators are separately configured to: receive an optical signal and a loaded electrical modulation signal, and modulate the optical signal based on the electrical modulation signal, to obtain a first modulated optical signal and a second modulated optical signal. The first adjustment module is further configured to adjust a phase of the modulated optical signal or an optical path to the beam combiner. The beam combiner is configured to: combine the first modulated optical signal obtained after the adjustment and the second modulated optical signal, and output a combined signal.

Abstract: An example optical receiver may have an optical receiver front-end, four slicers, and a logic block. The optical receiver front-end may include a transimpedance amplifier to convert a photodiode output signal to a voltage signal. Three of the slicers may be data slicers, and one of the slicers may be an edge slicer. The slicers may each: shift the voltage signal based on an offset voltage set for the respective slicer, determine whether the shifted voltage signal is greater than a threshold value and generate a number of comparison signals based on the determining, and generate multiple digital signals by demuxing the comparison signals. The logic block may perform PAM-4 to binary decoding based on the data signals output by the data slicers and clock-and-data-recovery based on the digital signals output by the edge slicer.

Abstract: An optical fiber that communicates in a predetermined communication band includes: a signal light propagation core that propagates light beams of up to (x+1)-th order LP mode, where x is an integer of two or more; and a coupler that propagates a light beam that is: coupled with a light beam of the (x+1)-th order LP mode propagating through the signal light propagation core, and suppressed from being coupled with light beams of up to the x-th order LP mode propagating through the signal light propagation core, wherein, mode coupling of the light beams of up to the x-th order LP mode propagating through the signal light propagation core is performed, and mode coupling between the light beam of the x-th order LP mode and the light beam of (x+1)-th order LP mode is suppressed.

Abstract: An optical module has an optical amplifier that amplifies an optical signal in which multiple wavelengths are multiplexed, an optical demultiplexer that separates the multiple wavelengths from the optical signal having been amplified by the optical amplifier, a first photodetector that monitors the optical signal at an input side of the optical amplifier, a second photodetector that monitors each of the multiple wavelengths at an output side of the optical demultiplexer, and a control circuit that controls a center wavelength of a filter of the optical demultiplexer based upon a first output from the first photodetector and a second output from the second photodetector.

Abstract: The system and method for secure optical communication, laser communication, and target designation. The system locks lasers at an absolute frequency reference and uses frequency tuning, frequency hopping, and frequency encoding techniques for optical communications. The system encodes information in the frequency context. An optional notch filter is used on a receiver to reduce “blinding” or saturation by adversaries. The system hops frequencies around an atomic reference. In some cases the system uses a frequency comb and a comb line of the second.

Abstract: A system and method that enforces one or more policy rules on user-allocated bandwidth portions of the overall system bandwidth, for example in an optical fiber transmission system. The policy rules may limit, for example, the range of optical wavelengths, the acceptable range on the output-power-spectral density and/or the total per-band optical power within the user-allocated bandwidth that a user may provide on the system. The system may include one or more user control units that receives respective user output signals and applies all policy rules. The resulting optical output(s) of the UCU(s) may be provided an optical transmission path for transmission to a receiving terminal. In the receiving terminal, one or more UCU(s) may apply receiver policy rules, for instance by limiting the range of wavelengths transmitted to a receive subsystem.

Abstract: This invention relates to an emitter for an optical communication system such as a Li-Fi system. This emitter comprises an M-PAM modulator and a conversion module to convert an M-PAM symbol into a plurality of logical outputs. It also comprises a plurality of branches in parallel, each branch comprising a switched current source mounted in series with the optical source, each switched current source being controlled by a logical output from the conversion module.

Abstract: Techniques for transmitting an optical signal through optical fiber with an improved cost effective stimulated Brillouin scattering (SBS) suppression include externally modulating a light beam emitted from a light source with a high frequency signal. The light beam is also modulated externally with an RF information-carrying signal. The high frequency signals are at least twice a highest frequency of the RF signal. The high frequency signals modulating the light source can be gain and phase adjusted by the first set of gain and phase control circuit to achieve a targeted spectrum shape. The adjusted high frequency signals then are split, providing a portion of the split signals to modulate the light source and another portion of the split signals to the second set of phase and gain control circuit for adjusting a phase/gain.

Abstract: A light data communication link device (50) for use in a magnetic resonance examination system (10) comprises a first light emitter and receiver unit (52) and a second light emitter and receiver unit (76). A light generating member (54), a first optical waveguide (62) and a light diffuser (58) of the first light emitter and receiver unit (52), a distance in space between the light diffuser (58) and a converging lens (84) of the second light emitter and receiver unit (76), and the converging lens (84), a second optical waveguide (88) and a light receiving member (80) of the second light emitter and receiver unit (76) form a first optical pathway (90) for data communication.

Abstract: Disclosed is network management technology for an optical line terminal. The optical line terminal allocates a line identifier according to a line length from each port to an end thereof. Terminal connection information is managed such that a corresponding line identifier is mapped to a measured line length to an optical network terminal. Service settings for an optical network terminal are managed by the line identifier.

Abstract: The invention relates to a wireless communication device which uses light, comprising at least: a light source emitting a modulated light signal; a photovoltaic module capable of receiving said modulated light signal; and an analog-to-digital converter electrically connected to the output terminals of said photovoltaic module, making it possible to convert the analog signal output by the photovoltaic module into a digital signal; characterised in that it also comprises a means for polarising said photovoltaic module making it possible to generate a polarisation voltage applied to the terminals of said photovoltaic module, and a management module capable of optimising said polarisation voltage into a threshold voltage corresponding to an improved signal-to-noise ratio and communication bandwidth.

Abstract: A monitoring system includes optical sensors disposed on one or more fiber optic waveguides. Each optical sensor is spaced apart from other optical sensors and is disposed at a location along a route defined by a transportation structure that supports a moveable conveyance. The plurality of optical sensors are mechanically coupled to one or both of the transportation structure and the moveable conveyance. Each optical sensor provides an optical output signal responsive to vibrational emissions of one or both of the transportation structure and the conveyance. The monitoring system includes a detector unit configured to convert optical output signals from the optical sensors to electrical signals. A data acquisition controller synchronizes recordation of the electrical signals with movement of the conveyance.

Abstract: Embodiments of the present invention provide data transmission and receiving methods based on an orthogonal frequency division multiplexing technology, and an apparatus. According to the present invention, grouping and differential encoding are performed on multiple subcarriers, and further, carrier location adjustment is performed, so as to effectively improve non-linear tolerance of a multi-subcarrier system.

Abstract: An optical transceiver includes a transmitter including transmitter signal processing circuitry configured to receive a transmit signal and provide two drive voltage signals V1, V2 to a modulator configured to modulate a laser based thereon; and a receiver including i) optical couplers configured to coherently combine received signals with a Local Oscillator (LO) formed by the laser and provide the combined signals to photodetectors for balanced detection, and ii) receiver signal processing circuitry configured to demodulate outputs from the balanced detection, wherein the receiver signal processing circuitry comprises an analog front-end and digital back-end.

Abstract: A communication method for a serial communications unit converts reception serial data into reception parallel data, stores the reception parallel data in a memory unit, and calculates a reception delay time of a reception start timing at which reception of packets is started. In addition, the reception parallel data which is stored in the memory unit is read out, and transmission parallel data, in which a transmission delay time of a transmission start timing at which transmission of packets is started is controlled so that a delay time from the reception start timing of packets and until transmission of packets is started is made constant, is output in synchronism with a transmission parallel clock pulse signal, and the output transmission parallel data is converted into transmission serial data and then is transmitted.

Abstract: A subscriber station for a bus system, and a method for improving the error tolerance of a subscriber station of a bus system, are presented. The subscriber station encompasses a transmission/reception device for transmitting a signal via the bus system to a further subscriber station and for receiving a signal via the bus system, in which exclusive, collision-free access by a subscriber station to a bus line of the bus system is guaranteed at least at times; and a modification device for modifying the transmission properties of a transmission path of the transmission/reception device and/or the reception properties of a reception path of the transmission/reception device.

Abstract: An optical transmitter includes: a driving circuit that includes drivers each corresponding to a configuration bit of an input electrical data sequence; a MZ optical modulator that includes a first phase shifter provided in an arm and a second phase shifter provided in an arm; first capacitance elements that are electrically connected between the driving unit and the first phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a first multilevel signal to be supplied to the first phase shifter; and second capacitance elements that are electrically connected between the driving circuit and the second phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a second multilevel signal to be supplied to the second phase shifter.

Abstract: Carrier suppression (CS-M-PAM) may be applied to M-PAM modulated optical signals to improve transmission reach. Additional rescaling of CS-M-PAM, referred to as adaptive CS-M-PAM, may further improve transmission reach by reducing low level symbol interference.

Abstract: A transmitter optical module that implements with two or more laser diodes (LDs) therein is disclosed. The LDs are mounted on a common sub-mount independent of driving circuits and driven by the driving circuits in the shunt-driving mode. The cathode of the LDs are independently, namely, isolated from the ground of the neighbor LDs, connected to the ground within the driving circuits but floated from the chassis ground.

Abstract: An optoelectronic configuration method is provided. The method includes determining a baseline link budget value for the VCSEL. The method applies a constant input value to a VCSEL and monitors the output of the VCSEL. The method calculates a first link budget value from the inputs and outputs of the VCSEL and compares the first link budget value with the baseline link budget value to determine either a pass state of the VCSEL or a fail state of the VCSEL. If a fail state of the VCSEL is determined, the method may iteratively apply modified inputs to the VCSEL until the desired relationship between the first link budget value and the baseline link budget value is obtained.

Abstract: The light power monitoring device includes: a first optical fiber; a second optical fiber connected to the first optical fiber; a low-refractive-index resin layer which covers (i) a connection between the first and the second optical fibers and (ii) a predetermined region of the second optical fiber which region extends from the connection toward a forward-propagating-light-output side; a high-refractive-index resin layer which covers a region of the second optical fiber which region is not covered by the low-refractive-index resin layer; and an outputted light detecting device which is provided at a position corresponding to an end of the low-refractive-index resin layer which end is located on the forward-propagating-light-output side of the second optical fiber or at a position which is away toward the forward-propagating-light-output side of the second optical fiber from the position corresponding to the end of the low-refractive-index resin layer.

Abstract: An optical transmitter has an optical modulator having Mach-Zehnder interferometers, modulator drivers configured to drive the optical modulator by a drive signal, a low frequency generator configured to generated a low frequency signal that changes a ratio of a driving amplitude with respect to a half-wave voltage of the optical modulator, a photodetector configured to detect a portion of output light of the optical modulator, a detector configured to detect a low frequency component contained in a detected signal from the photodetector using the low frequency signal, and a bias voltage controller configured to control a bias voltage for the optical modulator such that the detected low frequency component becomes the maximum and in-phase with the superimposed low frequency signal.