Abstract: Systems and methods are disclosed for splicing crystal fibers to silica glass fibers. Embodiments of the present disclosure provide mechanically stable bonds with negligible optical transmission loss by splicing fibers through a thermally enhanced reaction bonding process at lower temperatures than the melting point of the crystal. In an embodiment, mixing of the materials at elevated temperatures forms a stable intermediary material which enhances strength and reduces the transmission losses.

Abstract: An optical coupling device including, in sequence, a focusing lens and an optical coupling network, the coupling device being symmetric with respect to a plane, the focusing lens formed in a core layer, as a front face, perpendicular to the plane, the optical coupling network including a plurality of trenches, formed on the front face, and convex in shape, the optical coupling network including, in sequence, a first sub-network and a contiguous second sub-network, respectively delimited, by a first contour and a second contour, the first and second contours extending in a divergent manner and convergent manner respectively.

Abstract: Described are various configurations of reduced crosstalk optical switches. Various embodiments can reduce or entirely eliminate crosstalk using a coupler that has a power-splitting ratio that compensates for amplitude imbalance caused by phase modulator attenuation. Some embodiments implement a plurality of phase modulators and couplers as part of a dilated switch network to increase overall bandwidth and further reduce potential for crosstalk.

Abstract: A system configured to a plurality of zones of an aircraft includes first and second connectors are in optical communication, an optical fiber, a first interrogator, and a controller. The optical fiber extends between the first and second connectors and includes a first timing fiber Bragg grating disposed in the optical fiber at a reference location of the optical fiber. The first interrogator is connected to the optical fiber and is configured to provide a first optical signal to the optical fiber and to receive a first timing signal from the optical fiber. The first timing fiber Bragg grating is configured to provide the first timing signal with information related to the first timing fiber Bragg grating from the first interrogator. The controller is operatively connected to the first interrogator and is configured to determine the reference location of the optical fiber.

Abstract: An optical connector includes a lens body including a lens portion, an optical conversion module, and a housing including an accommodation portion having a recessed portion, the optical conversion module combined with the lens body being fitted and assembled into the accommodation portion. The optical conversion module includes a light element disposed at a position facing the lens portion when combining the optical conversion module with the lens body. The housing includes a longitudinal support mechanism. The longitudinal support mechanism includes a reference surface and a pressing rib.

Abstract: A full-spectrum covering ultra wideband full-photonics based radar system comprising a signal transmitter, a transceiver module, and a signal receiver. The signal transmitter comprises a mode-locked laser, a first dispersion module, a first optical coupler, a second optical coupler, a first optical filter, a second dispersion module, a second optical filter, a first adjustable time delay module, a third optical coupler, an optical amplifier, and a first photodetector; the transceiver module comprises a band selector, a first electrical amplifier array, a T/R component array, an antenna array, and a second electrical amplifier array; the signal receiver comprises a third optical filter, a second adjustable time delay module, an electro-optical modulator, a third dispersion module, a second photodetector, an analog-digital conversion module, and a signal processing module.

Abstract: The present embodiment relates to a CC-MCF capable of generating sufficient mode coupling even with bending or twisting less. The CC-MCF includes two fiber parts having cores mutually directly or indirectly connected, each fiber part having a plurality of cores in which a pair of adjacent cores has a mode-coupling coefficient of 1 (1/m) or more. Each fiber part is provided with a transition section including a fiber end face and a stationary section adjacent to the transition section. In the stationary section, the MFD of each core is substantially constant in a fiber longitudinal direction, and in the transition section, the MFD of each core is continuously expanding from the stationary section to the fiber end face.

Abstract: Provided is a signal loopback circuit which, in order to loop back a monitoring signal in a relay device for relaying optical signals of a plurality of wavelength bands, connects between a channel of first direction and a channel of second direction through which an optical signal of first wavelength band and an optical signal of second wavelength band are transmitted, wherein the signal loopback circuit is provided with a first coupler for branching the optical signal on the channel of first direction, a first filter for extracting at least one of a monitoring signal of first wavelength band and a monitoring signal of second wavelength band that are used in the channel of first direction from the optical signal branched by the first coupler, and a second coupler for causing the monitoring signal extracted by the first filter to be joined to the channel of the second direction.

Abstract: Spectrum sensors can be continuously calibrated in a manufacturing environment employing a continuously moving platform that carries the spectrum sensors in combination with spatially separated light spectra illuminating a region of the platform. A plurality of spectrum sensors, each including multiple sensor pixels, can be placed on the platform. The spatially separated light spectra can be illuminated over an area of the platform. The plurality of spectrum sensors can be moved with the platform through a region of the spatially separated light spectrum. Each sensor pixel for each of the plurality of spectrum sensors can be calibrated based on response of each spectral channel during passage through the spatially separated light spectra. The entire spectra from a light source can be employed simultaneously to calibrate multiple spectrum sensors in the manufacturing environment.

Abstract: In order to provide a compact and low power consumption optical repeater capable of amplifying a plurality of wavelength ranges, the optical repeater is provided with: an excitation means which generates excitation light in a single wavelength range; a first light amplification means which is excited by the excitation light and the amplification band of which is a first wavelength range; and a second light amplification means which is excited by the excitation light and the amplification band of which is a second wavelength range different from the first wavelength range.

Abstract: An optical demultiplexer/multiplexer, comprising: a multimode interference waveguide; at least one first coupling waveguide which meets the multimode interference waveguide at least one first location and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations which are spaced in a direction of transmission in relation to the at least one first location, with the at least one first coupling waveguide and the second coupling waveguides together with the multimode interference waveguide providing a first angled multimode interferometer which operates to demultiplex a first optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a first optical signal having optical channels of the plurality of wavelengths; at least one third coupling waveguide which meets the multimode interference waveguide at least one third location and a plurality of fourth coupling waveguides whi

Abstract: An optical coupler array can include an elongated optical element having a coupler housing structure and at least one longitudinal waveguide embedded in said housing structure. The housing structure can have an outer cross sectional shape comprising a first side comprising one or more curved portions and a second side comprising one or more flat portions. The second side can be disposed at a distance from the at least one longitudinal waveguide such that waveguiding properties are preserved and not disturbed.

Abstract: An apparatus comprising a polarization beam splitter optically coupled to a first light path and a second light path and configured to receive a CW light having a plurality of wavelengths, forward a first light beam of the CW light along the first light path, and forward a second light beam of the CW light along the second light path. A first multiplexer coupled to the first light path and configured to de-multiplex the first light beam into a first plurality of channels each corresponding to one of the plurality of wavelengths. A second multiplexer coupled to the second light path and configured to de-multiplex the second light beam into a second plurality of channels each corresponding to one of the plurality of wavelengths. A modulator coupled to the first multiplexer and the second multiplexer and configured to modulate the first plurality of channels and the second plurality of channels.

Abstract: A system and method for generating copies of a signal includes a first radiation source configured for providing a plurality of pump radiation beams, a second radiation source configured for providing a signal radiation beam, and a second-order nonlinear optical medium to receive the plurality of pump radiation beams from the first radiation source and the signal radiation beam from the second radiation source and to emit a plurality of idlers, where the plurality of idlers are low-noise copies of the signal.

Abstract: There is provided a method for controlling an electronic device, the method comprising starting control of emission of laser light from at least one light-emitting part of a receptacle, wherein the at least one light-emitting part comprises an optical member and a lens associated with the optical member, the start of the control of the emission of the laser light is based on a flow of current from a partner side electronic device to at least two electrical contacts of the receptacle and detection of a connection of a cable to the receptacle, and the at least one light-emitting part emits the laser light to communicate with the partner side electronic device.

Abstract: Practical silicon-based light sources are still missing, despite the progress in germanium lasers, because both silicon and germanium are indirect-band semiconductors and inefficient at light generation. A tunable and single mode external cavity laser comprising: a gain medium for generating light between a reflective surface at one end of the gain medium; and a wavelength selective reflector at the other end of a laser cavity. A splitter disposed in the laser cavity includes an input port optically coupled to the gain medium, an input/output port optically coupled to the wavelength selective reflector, and an output port for outputting laser light at selected wavelengths. The wavelength selective reflector reflects light of one or more selected periodic wavelengths back to the gain medium via the input/output port, and passes light of non-selected wavelengths out of the laser cavity.

Abstract: A component locating apparatus for alignment of components on opposite sides of a structural wall includes a source magnet and a clone magnet. The source magnet has a magnetic centroid positioned relative to a locating feature and is successively held against the first side of the structural wall at a plurality of spaced apart source positions. The clone magnet has a marking opening at a magnetic centroid and is magnetically held against the second side of the structural wall by an attractive magnetic force at clone positions corresponding to the source positions. The magnetic centroids are aligned by the attractive magnetic force and the marking opening allows an operator to mark the second side of the structural wall at the magnetic centroid of the clone magnet at each of the clone positions to mirror, on the second side, the source positions corresponding to the component locating template.

Abstract: An optical wireless communications receiver includes a set of photodetectors and signal processing circuitry that receive and process optical communications signals to generate receive data. The receiver includes a spatial light modulator (SLM) and associated SLM controller. The SLM receives an incident optical communications signals from remote optical transmitters and selectively directs the received optical communications signals to the photodetectors to realize an SLM pattern according to SLM control signals from the SLM controller. A system controller establishes the SLM pattern and communicates a description of it to the SLM controller for use in generating the SLM control signals. The receiver may be used in a variety of applications, including so-called visible-light communications or VLC, in which data is transmitted over an optical link using light in the visible spectrum.

Abstract: A reflecting module for optical image stabilization (OIS) includes: a housing; a moving holder supported in the housing by an elastic member; a reflecting member provided on the moving holder; and a driving part configured to provide driving force to the moving holder, wherein the driving part includes: two magnets having a shorter length in a first axial direction than in a second axial direction perpendicular to the first axial direction and disposed on the moving holder to be spaced apart from each other in the first axial direction; and four or more coils disposed on the housing, the four or more coils being disposed as two sets, respectively including a first set of two or more coils aligned in the second axial direction and spaced apart from each other in the first axial direction to face the two magnets, respectively.

Abstract: This optical receptacle is provided with: a first optical surface; a second optical surface; a first recess; a second recess; an inclined surface; insertion holes; through holes; and reference parts. The second optical surface and the inclined surface face each other at inside surfaces of the first recess. The inclined surface is inclined so as to extend away from the second optical surface as the inclined surface approaches an opening of the first recess. First openings which are open at the inclined surface and second openings which are open at an inside surface of the second recess are provided at both ends of the linear insertion holes. The thorough holes face the second openings on the central axes of the insertion holes. The reference parts are provided to the surface at the side at which the first recess and the second recess are open.

Abstract: A sensing device is used for measuring physical characteristics. The sensing device may include an optical fiber disposed in a tube. The optical fiber may have a section containing a fiber Bragg grating (FBG) sensor. A support member may be coupled to the ends of the section, such that the section includes a length greater than a length of the portion of the support member disposed between the ends of the section. The support member is configured to isolate the FBG sensor from strain in the optical fiber.

Abstract: Provided is an optical probe that includes an optical waveguide having a core layer and a cladding layer formed so as to cover the core layer, and a support member that supports an end portion of the optical waveguide. In the core layer, an optical waveguide core and a diffraction grating are provided. The diffraction grating is provided at an end of the optical waveguide core, has an input/output surface through which light is output to the outside or input from the outside, and converts the optical axis direction in a range between a light propagation direction in which light is propagated through the optical waveguide core and the input/output direction of light to/from the input/output surface. The support member supports the diffraction grating in such a manner that the input/output surface faces toward a predetermined direction.

Abstract: A demultiplexing unit that is provided in an optical device and performs demultiplexing into a plurality of optical signals having wavelengths different from each other includes a plurality of optical filters that are coupled in multiple stages and in which a period of a peak wavelength of a transmission spectrum differs among different stages, a monitoring optical filter coupled to one of the plurality of optical filters, a monitoring photodetector coupled to the output side of the monitoring optical filter, and a plurality of wavelength adjustment units that are provided individually for the plurality of optical filters and the monitoring optical filter and cause wavelength shifts of an equal amount in a same direction.

Abstract: A beam steering device and a system employing the same are provided. The beam steering device includes: waveguides provided on a substrate to form channels through which light is transmitted; a modulators provided on the waveguides and configured to change, according to electrical signals, a phase of the light by changing a refractive index of the light which passes through the waveguides; and a driving circuit configured to provide the electrical signals to the modulators to drive the modulators.

Abstract: The invention discloses a cell culture and experiment device used in the field of biological and genetic engineering experiment apparatus, comprising a cent distribution compartment, a culture compartment, a treatment compartment, and pipelines for delivering liquid between the central distribution compartment and the culture compartment and between the central distribution compartment and the treatment compartment. The central distribution compartment is equipped with a distribution chamber and a piston which can be moved forward and backward in the distribution chamber to alter the working volume of the distribution chamber. At the bottom of the distribution chamber, the central distribution compartment is equipped with a distribution valve controlling the connectivity between the distribution chamber and any of the channels.

Abstract: Imaging systems and method of optical imaging. One example of an imaging system includes an optical scanning subsystem including an optical source and a waveguide, the waveguide being configured to direct optical radiation generated by the optical source over an area of a scene, a detection subsystem including an optical sensor configured to collect reflected optical radiation from the area of the scene, and a fused fiber focusing assembly including a fused fiber bundle, a plurality of lenses coupled together and positioned to receive and focus the reflected optical radiation from the area of the scene directly onto the fused fiber bundle, a microlens array interposed between the fused fiber bundle and the optical sensor and positioned to receive the reflected optical radiation from the fused fiber bundle, and a focusing lens positioned to direct the reflected optical radiation from the microlens array onto the optical sensor.

Abstract: Bi-directional data center architectures employing a jacketless trunk cable are disclosed. The bi-directional data center architecture includes first and second coupling panels respectively operably connected to first and second trunk cables, wherein the first and second coupling panels respectively have first adapters and second adapters. The architecture also includes a plurality of sub-racks having sub-rack adapters, and a jacketless trunk cable that includes a plurality of sub-units, with each sub-unit carrying one or more optical fibers. The plurality of sub-units are configured to optically connect corresponding first and second adapters of the first and second coupling panels to the sub-rack adapters such that every optical fiber in each sub-unit is used to establish an optical connection.

Abstract: An optical interconnect structure and method are provided. The optical interconnect structure includes a plate on which a mirror is formed. The optical interconnect structure further includes a waveguide structure comprising a waveguide core and an opening. The plate is mounted on the waveguide structure such the mirror is inserted in the opening for light coupling (i) from the waveguide core and to an optical element positioned on the plate and (ii) to the waveguide core from the optical element positioned on the plate.

Abstract: A mode converter provided in the present invention includes an input multimode waveguide, an output multimode waveguide, and a first conversion waveguide, where the input multimode waveguide is configured to receive a first signal which mode is a first mode; the first conversion waveguide has an input coupling waveguide with a first effective refractive index, and has an output coupling waveguide with a second effective refractive index; the first conversion waveguide is configured to perform, by using the input coupling waveguide, evanescent wave coupling on the first signal that is in the first mode and that is transmitted in the input multimode waveguide, and couple the first signal to the second mode of the output multimode waveguide by using the output coupling waveguide, so as to obtain the first signal in the second mode; and the output multimode waveguide is configured to output the first signal in the second mode.

Abstract: A quantum error-correction technique includes applying a first set of two-qubit gates to qubits in a lattice cell, and applying a second, different set of two-qubit gates to the qubits in the lattice cell. The qubits in the lattice cell include data qubits and ancilla qubits, and the ancilla qubits reside between respective nearest-neighbor pairs of the data qubits. After the first and second sets of two-qubit gates have been applied, measurement outcomes of the ancilla qubits are obtained, and the parity of the measurement outcomes is determined.

Abstract: System and method utilizing a reconfigurable in real-time phase-modulating diffractive device (in a specific case—a 2D array of micro-mirror elements) in conjunction with another diffractive element (active or passive) to spatially steer a beam of polychromatic light such that light reaches the identified target without being substantially angularly dispersed.

Abstract: A modified directional coupler structure is used to provide a controllable time delay or phase shift for radiation propagating through the structure. A longitudinal displacement of the interaction region of the directional coupler relative to one or both of the waveguides of the directional coupler provides this effect. Double flexure arrangements can be used to provide longitudinal displacement with substantially no corresponding lateral displacement (or vice versa). In some embodiments, lateral and longitudinal displacement of the waveguides of the directional coupler are independently adjustable to provide full control of the power splitting and phase shift/time delay of the directional coupler.

Abstract: There is provided an opto-electric hybrid board including an optical waveguide including a linear core held between first and second cladding layers; electrical interconnect lines formed on a surface of the first cladding layer, with a light-permeable insulative layer therebetween; and a light-emitting element and a light-receiving element mounted on mounting pads of the electrical interconnect lines. Light reflecting surfaces for reflecting light are formed in end portions of the core. The light reflecting surfaces are concave surfaces curved in at least one of the width direction and the thickness direction of the core, and having a radius of curvature greater than 50 ?m and less than 1500 ?m as measured in the width direction of the core and a radius of curvature greater than 200 ?m and less than 1500 ?m as measured in the thickness direction of the core.

Abstract: A wavelength division multiplexing (WDM) transceiver module comprising an optical port and an optical modulator is disclosed herein. The optical port includes a data transmit and receive optical fiber connector and a laser source-in optical fiber connector. The laser source-in optical fiber connector is configured to couple to a laser source external to the WDM transceiver module, and provide polarization alignment for a polarization-maintaining fiber. The optical modulator is configured to receive a laser output from the external laser source via the polarization-maintaining fiber and modulate the laser output based on analog electrical signals generated by a digital signal processor. The WDM transceiver module may not including an onboard laser source.

Abstract: An example photonic integrated circuit includes a transmitter circuit with a optical communication path to an optical coupler configured to couple with an optical fiber. The optical communication path has a propagation direction away from the transmitter circuit and towards the optical coupler. A counter-propagating tap diverts light sent by a light source backward against the propagation direction of the optical communication path. A photodiode receives the diverted light and measures its power level. The photodiode generates a feedback signal for the optical coupler and provides the feedback signal to the optical coupler. The optical coupler receives the feedback signal and adjusts a coupling alignment of the optical communication path to the optical fiber based on the feedback signal, which indicates the measured power level of the diverted counter-propagating light.

Abstract: The disclosure relates to a tunable microring resonator, comprising a primary waveguide having first and second ends, a plurality of secondary waveguides each having a different length and each having first and second ends and a Micro-Electro-Mechanical System (MEMS) adjustable to optically couple at least a first end of the primary waveguide with a first respective end of a selected secondary waveguide thereby allowing light to circulate within the tunable microring resonator.

Abstract: An optical signal processing device with a transponder aggregator function by which theoretical loss is not increased even if the number of necessary transponders is increased. Optical signals inputted from input ports are inputted to a PLC. The PLC has SBTs. The input ports are connected to the input-end SBT, and a plane wave is outputted from an output end of the PLC to the space side at an angle different for each input port. Optical signals outputted by the PLC are changed in their optical paths on the x-z plane by a cylindrical lens (Lsp) designed to refract optical signals in the x-axis direction, and are reflected by an LCOS at different regions corresponding to the positions of the input port. The reflected optical signals are incident on the output-end SBTs on the PLC, and are outputted to output ports via demultiplex parts.

Abstract: Spatial division multiplexing (SDM) allows multiple optical signals to be multiplexed onto a single optical link. Performance of SDM systems may be improved by monitoring performance metrics indicative of crosstalk between the spatially multiplexed signals and adjusting at least one transmission characteristic of one or more of the multiplexed signals in order to reduce the impact of the intermodal crosstalk.

Abstract: There is provided an electronic device including: a receptacle comprising at least two electrical contacts and a plurality of a light-emitting parts configured to emit laser light for performing communication by light to a sink device; and a light emission control part configured to control emission of laser light from the plurality of light-emitting parts, wherein the light emission control parts starts control of the emission of the laser light from the plurality of light-emitting parts by a current when a cable is connected to the receptacle and the current flow to the electrical contacts from the sink device.

Abstract: An optical receiver, used in wavelength-division multiplexing, has multiple photodetectors per channel. The optical receiver comprises a demultiplexer to separate incoming light into different output waveguides, one output waveguide for each channel. A splitter is used in each output waveguide to split each output waveguide into two or more branches. A separate photodetector is coupled with each branch so that two or more photodetectors are used to measure each channel.

Abstract: The invention relates to a device for forming laser pulses comprising: an input for a pulsed laser beam; a spatial phase modulator (300), arranged on the trajectory of said pulsed laser beam so as to be illuminated thereby; a control means designed to configure said spatial phase modulator so as to emulate a diffraction grating (3, 3?) having a diffraction efficiency that varies along one spatial direction (s) identified by the intersection of the modulator surface with the diffraction plane (xz); and spatial filtering means (5) for a light beam diffracted by said grating; whereby a laser pulse (P1) at the device input is converted to a train of elementary output pulses (PS) having temporal intensity and/or phase and/or polarization modulation. The invention further relates to a laser pulse forming process based on the use of such a device.

Abstract: A high-speed multi-channel optical transmitter module includes a plurality of laser-diode (LD) components, a plurality of photo-diode (PD) components, an MT ferrule, and a waveguide component. These components are firstly packaged as sub-modules individually, and then these sub-modules are packaged to form the high-speed multi-channel optical transmitter module. Therefore, the amount of individual components contained in the module is decreased, the complexity of structure is simplified, the precision of positioning is increased, such that the time and labors required in the assembling and packaging processes can be decreased, and the defect-free rate of products can be increased.

Abstract: A system and method for backchannel closed loop feedback for channel equalization over Ethernet. Closed loop backchannel feedback for real-time transmitter adaptive equalization is provided for a pair of non-ideal duplex communication channels. The real-time transmitter adaptive equalization enables use of low cost relaxed specification transmitter modules at high data rates.

Abstract: A switch module includes a switch integrated circuit (IC), an InP chip, and a planar lightwave circuit (PLC). The InP chip may include a plurality of light sources, an optical splitter, and a plurality of modulators.

Abstract: A high-speed interrogation system is provided for interferometric sensors, one example of which is an EFPI sensor, that operates based on spectral interference. The system uses a two mode operation that includes a lower speed, accurate absolute measurement mode and a higher speed, relative measurement mode. The system achieves greater overall measurement accuracy and speed than known sensor interrogation approaches.

Abstract: A network appliance may include a signal splitter that splits an incoming signal into multiple portions. The signal splitter can direct one portion of the incoming signal to a switching fabric and another portion of the incoming signal to an optical switch. By monitoring the power intensity of the portion of the incoming signal received by the switching fabric, the network appliance can seamlessly switch between a bypass traffic path and a pass-through traffic path without losing network traffic caused by gaps in network connectivity. Such a configuration also enables the network appliance to maintain an accurate record of the logical connectivity state even when the network appliance is in the bypass state (i.e., when network traffic bypasses the switching fabric of the network appliance).

Abstract: A head-mounted display apparatus includes a display, a couple-in optics module and a couple-out optics module. The display is arranged for displaying at least an image. The couple-in optics module is arranged for receiving the image from the display and directing the received image to another direction. The couple-out optics module is arranged for receiving the directed image from the couple-in optics module to generate an output image directly to a human eye when a user wears the head-mounted display apparatus. In addition, an aspect ratio of the image generated from display is different from an aspect ratio of the output image.

Abstract: A multiplexer/demultiplexer for at least two wavelengths in O-band. The multiplexer/demultiplexer includes a silicon waveguide block having a first port, a second/third port respectively in bar/cross position at an opposing end plane relative to the first port. The silicon waveguide block is configured to provide a general interference excitation of a light wave of a first wavelength and a second wavelength respectively selected from two windows in O-band. The light wave is either inputted via the first port and split into a first output light of the first wavelength out of the second port and a second output light of the second wavelength out of the third port, or is combined of a first input light of the first wavelength from the second port and a second input light of the second wavelength from the third port and outputted via the first port with both wavelengths.

Abstract: The inventive configurable optical fiber polarization mode coupler is capable of providing a low-loss, high-coupling coefficient interface with high accuracy and easy alignment between a plurality of optical fibers (or other optical devices) with a first channel-to-channel spacing, and an optical device having a plurality of closely-spaced waveguide interfaces with a second channel-to-channel spacing, where each end of the optical fiber coupler array is configurable to have different channel-to-channel spacing, each matched to a corresponding one of the first and second channel-to-channel spacing, and that are preferably optimized for use with photonic integrated circuits, such as coupling to dense optical input/output interfaces, wafer-level testing, etc.

Abstract: A pressure sensing system includes a circuit board, a case, a cover layer, a plurality of light emitters, and a photo detector. The circuit board has a top surface and a bottom surface. The case is located near the bottom surface of the circuit board. The distance between circuit board and the case decreases when the circuit board is subjected to a pressure. The cover layer covers a part of the top surface and a part of the bottom surface, wherein a part of the top surface which is not covered by the cover layer includes a plurality of first passing zone and a second passing zone, and a part of the bottom surface which is not covered by the cover layer includes a plurality of bottom passing zone. The light emitters are located on the first passing zone, respectively, and the photo detector is located on the second passing zone.