1300 results about "Extinction ratio" patented technology

The transmission system includes a first electro-optical modulator adapted to supply in response to an input electrical signal a controlled phase optical signal having an optical power modulated between low levels and high levels and a phase shift within each time cell that contains a low power level. To make it more flexible to use, the system includes a second electro-optical modulator controlled by the input signal and optically coupled to the first electro-optical modulator to apply to said controlled phase optical signal complementary power and/or phase modulation so as respectively to modify its extinction ratio and/or to apply a transient "chirp" to it.

A method of manufacturing a polarizing plate of a resonance absorption effect type wherein plural bar-like polarizing members are arranged in a light-transmittable polarizing matrix layer with major axes thereof orienting in a constant direction. The method includes a preparing process of a forming die for preparing a forming die having a concavoconvex pattern corresponding to a layout pattern of the bar-like polarizing members, a forming process of a concavoconvex pattern on a resin layer for forming a resin layer directly or indirectly on a substrate and pressing the forming die onto the resin layer so as to form a concavoconvex pattern on the resin layer, a forming process of bar-like polarizing members for forming the bar-like polarizing members in the foregoing layout pattern using the concavoconvex pattern of the resin layer, and a forming process of a polarizing matrix layer for forming the light-transmittable polarizing matrix layer so as to bury the formed bar-like polarizing members. Accordingly, the polarizing plate of the resonance absorption effect type can be obtained, which is low in price, massproducible, high in extinction ratio, high in performance and high in reliability.

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50/50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.

The invention provides a method and device for detecting a polarization extinction ratio of an optical polarizer. The detection method comprises the following steps of: making linear polarized light incident along a principal axis of an optical polarizer to be detected, and obtaining two light signals on two orthogonal optical axes at an outgoing end due to polarization crosstalk; interfering and carrying out photoelectric conversion and data acquisition on interfering light signals to obtain one group of discrete voltage signal values reflecting the interfering light intensity signals; and calculating coupling intensity h at each coupling spot based on a formula (1), and calculating an extinction ratio of the optical polarizer to be detected based on a formula (2). The device sequentially comprises a light source, an isolator module, a polarization module, the optical polarizer to be detected, a projection direction regulating module, an interferometer module, a data acquisition module and a central processor module. The invention has the advantage that the coupling intensity of the coupling spots is detected to induce the polarization extinction ratio, so that the measurement result is accurate. The invention is suitable for various optical polarizers, such as polarization maintaining fibers, polarization maintaining fiber couplers, polarizers and the like and has certain universality.

A programmable spatial filter for use as a Fourier plane filter in dark field wafer inspection systems, based on the use of MEMS (Micro-Electro-Mechanical Systems) devices. In comparison with prior art systems, especially those using LCD's, the use of MEMS devices provide a number of potential advantages, including good transmission in the UV, a high fill factor, polarization independence and a high extinction ratio since the shutter is opaque when closed. The MEMS devices can be flap devices, artificial eyelid, or double shutter devices. Additionally, a novel spatial light modulator (SLM) assembly having a double layer of SLM arrays is described, in which the fill factor is increased in comparison to a single layer SLM using the same devices, by positioning the dead areas of the elements of both arrays collinearly in the modulated beam. This SLM assembly can be implemented using pixelated LCD arrays or MEMS arrays.

The invention discloses an optical module and an adjusting method of a working temperature of a laser thereof. The method comprises determining a current environment temperature according to an obtained temperature value after a micro controller unit (MCU) in the optical module obtains the temperature value detected by a temperature sensor; determining a working temperature set value corresponding to the current environment temperature and a BIAS current set value; controlling a driving circuit to output corresponding BIAS current according to the determined working temperature set value; and controlling a thermoelectric cooler (TEC) control circuit to adjust the working temperature of the laser to be a corresponding temperature according to the determined working temperature set value. Due to the facts that the working temperature of the laser is allowed to be changed correspondingly along with the environment temperature within a certain range and BIAS current adjustment is simultaneously adopted to serve as a compensation means to enable optical power and extinction ratio to be constant, the difference between the working temperature of the laser and the environment temperature is reduced, heating or refrigeration current provided for a TEC is reduced, and the goal of reducing power consumption is achieved.

A method of maintaining desirable optical performance of optical emitters over temperature variations is disclosed. The optical performance of an optical emitter in terms of power, extinction ratio, jitter, mask margin and general fiber optic transmitter eye quality can be maintained by the present invention over a wide range of temperatures. Advantageously, the present invention enables the use of inexpensive optical emitters in optoelectronic transceivers and optoelectronic transmitters.

The invention provides an active optical module multi-channel automatic test system and a method. optimal signals emitted by a tested optical module are monitored, and indexes of the incident light power, emission current, bias current, temperature, voltage, extinction ratio, eye diagram allowance, crossing point, OMA (optical modulation amplitude) etc. are measured and calculated; if the above indexes are all in accordance with the standard, the sensitivity of the optical module is tested, the emission optical power of the tested module is enabled to reach the sensitivity of the test standard via the adjustment of an attenuator, and error code tests are conducted; and if there is no error code, indexes of alarm value and alarm recovery etc. of the optical module are tested. According to the test system, an error detector, an optical module test board, an optical power meter, and the attenuator employed by the test system are all multi-channel devices, an optical switch and an optical splitter are combined for time-sharing multiplexing of one oscilloscope, at least 8 modules can be simultaneously tested, the utilization rate of the oscilloscope and the test efficiency of the optical module are greatly optimized, the equipment cost and the manual cost are reduced, and automatic and batch production of the optical modules is realized.

The invention discloses a polaroid sheet with a subwavelength grating structure, which comprises a transparent substrate, a dielectric grating, a first metal layer and a second metal layer. The dielectric grating is provided with ridges and grooves which are periodically arranged at intervals, the first metal layer is covered on the ridges of the dielectric grating, the second metal layer is covered in the grooves of the dielectric grating, and the period of the dielectric grating is less than the wavelength of incident light. The invention is characterized in that: a high refractive index dielectric layer is arranged between the transparent substrate and the dielectric grating, and the refractive index of the high refractive index dielectric layer is between 1.6 and 2.4. The transmission efficiency and the extinction ratio of TM light of the polaroid sheet are improved by adding the high refractive index dielectric layer between the transparent substrate and the dielectric grating. In the whole visible light waveband, the polaroid sheet has high transmission efficiency, high extinction ratio, and wide incident angle range. In the process, a nano-imprint technique is adopted to process and produce, the production process is simple and convenient and is easy to operate, an etching process is not needed, and the processing cost is reduced.

An optical modulator is formed to include an adjustable drive arrangement for dynamically adjusting the effective length of the optical signals path(s) within the modulator. Each modulator arm is partitioned into a plurality of segments, with each segment coupled to a separate electrical signal driver. Therefore, the effective length of each modulator arm will be a function of the number of drivers that are activated for each arm at any given point in time. A feedback arrangement may be used with the plurality of drivers to dynamically adjust the operation of the modulator by measuring the extinction ratio as a function of optical power, turning “on” or “off” individual drivers accordingly.

The invention discloses a laser driver and a temperature compensation circuit thereof. The temperature compensation circuit comprises a benchmark voltage generation unit, a benchmark current generation unit, a reference voltage generation unit, and a compensation current generation unit, wherein the benchmark voltage generation unit generates a benchmark voltage which increases with the increase of the temperature; the benchmark current generation unit is connected with the benchmark voltage generation unit and outputs benchmark current which increases with the increase of the benchmark voltage; the reference voltage generation unit generates a reference voltage which increases with the increase of the temperature; the compensation current generation unit is connected with the reference voltage generation unit, obtains the compensation threshold temperature according to the reference voltage, and outputs compensation current when the temperature is higher than or equal to the compensation threshold temperature; and the benchmark current and the compensation current are overlapped to form benchmark modulation current. The laser driver comprises the temperature compensation circuit and a bias current regulation circuit. An optical signal output by the laser can have constant extinction ratio by compensating modulation current of a laser through the temperature compensation circuit, and the laser can obtain steady output optical power by compensating bias current of the laser through the bias current regulation circuit.

The making process of lithium niobate modulator includes making substrate with lithium niobate crystal with proper crystal cutting direction and electric field utilizing direction; making light waveguide on the lithium niobate crystal; making modulating electrodes including central signal electrode and earth electrode and to form push-pull structure with the light waveguide; making microstrip matching structure in the input and output of the modulating electrodes; and setting buffering layer structure between the modulating electrode and light waveguide. Owing to the smart design of the modulating electrodes, the light waveguide and the matching structure in between, the lithium niobate modulator has high modulating rate, low insertion loss, high extinction ratio, low hemi-wave voltage, less electric reflection, and high reliability.

The invention relates to a sub-wavelength wire-grid polarizer, belongs to an optical polarizer, and in particular relates to a wire-grid polarizer. The polarizer aims to solve the problems that the prior wire-grid polarizer is low in transmission and extinction ratio. A wire stripe grid is arranged on a substrate; the surface of the wire stripe grid is provided with a protective layer; an interface of the substrate connected with the wire stripe grid is provided with a multi-layer dielectric film, and the other interface of the substrate is provided with a multi-layer dielectric anti-reflection film; and the multi-layer dielectric film is one of an anti-reflection film, a reflection film and a band pass filter film. Corresponding optical thin films are arranged on an incident light interface and an emergent light interface, so that the polarizer greatly improves the transmission and the polarization extinction ratio and solves the problems of low transmission and polarization extinction ratio in the prior polarizer; the polarizer can be separately used as an optical polarizer or an optical analyzer, and also can be used as a laser output coupling mirror, wherein the output of the laser is linearly polarized light with tunable wavelength. Moreover, the polarizer can be used in the fields such as optical measurement, optical communication, laser and the like.

Disclosed herein are methods, apparatus, and systems to achieve substantially constant optical power and/or extinction ratio for a semiconductor laser. In one aspect, a microcontroller of an optical transmitter may adjust an electrical current that is provided to a semiconductor laser based at least in part on a comparison of a first measured optical power of light emitted by the semiconductor laser and a predetermined target optical power. The microcontroller may then determine an electrical current that is capable of giving the semiconductor laser a substantially constant extinction ratio by evaluating an equation with the first measured optical power and a second optical power measured after the controller adjusts the electrical current.

A Q-modulated semiconductor laser comprises an optical gain section and an electro-absorptive modulator section, separated by a vertically etched air gap acting as a partially reflecting mirror. The modulator section is placed inside an anti-resonant Fabry-Perot cavity and acts as the rear reflector of the laser. The change of the absorption coefficient in the modulator section results in a change in the Q-factor of the laser, and consequently the lasing threshold and output power. Different embodiments are disclosed, which involve a distributed feedback (DFB) laser, a Fabry-Perot laser, a distributed Bragg reflector (DBR) laser, or a wavelength switchable multi-cavity laser. The integrated Q-modulated laser has advantages of high speed, high extinction ratio, low wavelength chirp and low cost.

A thin polarizer array and a wavelength plate array that are composed of micro regions having different optical axis directions and wavelength characteristics and have a high extinction ratio and a low insertion loss, and a polarization analyzer using them are disclosed. An array of micro periodic grooves is formed on a substrate, with the directions changed from one region to another. An alternating multilayer film formed by alternating a layer of high refractive index material such as Si or Ta2O5 and a layer of low refractive index material such as SiO2 is formed by bias sputtering. By selecting a condition that each layer maintains its periodic projecting/recessed shape, an array of photonic crystal polarizer is formed. By mounting this array of photonic crystal polarizer in a photodetector array, a polarization analyzer that is small, has no movable part, is composed of a small number of components, and enables high-precision measurement is constituted.

The invention discloses a spiral-like metal chiral metamaterial circular polarizer, which comprises a substrate, a transparent dielectric space layer firmly combined with the substrate and a spiral-like metal chiral micro structure array embedded in the transparent dielectric space layer, wherein the micro structure array comprises N periodically-arranged micro structure units, and N is more than 1 but no more than 106; the micro structure unit comprises m vertically-stacked metal arcs with the same size and with an angle of theta, the metal arcs are arranged rotarily around the same center, upper-layer metal arcs rotate for an angle of theta in relative to lower-layer metal arcs, theta is no less than 10 DEG but no more than 180 DEG, m is no less than 360/theta+1 but no more than 10, and tail ends of the upper-layer metal arcs and the lower-layer metal arcs are connected via metal cylinders to form a spiral-like shape. Compared with the traditional circular polarizer, the size is small, the waveband is wide, the extinction ratio is high, manufacturing of a micro circular polarization array can be realized, integration with a linear polarization structure uniwafer is even realized, a core polarization device is provided for full-Stokes vector real-time polarization imaging, and the spiral-like metal chiral metamaterial circular polarizer can be applied to fields such as polarization imaging detection, display and laser.

An automatic closed loop power control system is described for simultaneously adjusting an output power and an extinction ratio P₁/P₀ of a laser diode in order to maintain a desired average output power and a desired extinction ratio. The bias current component of a laser diode drive current is adjusted to compensate for changes in the average output power caused by ambient characteristics such as temperature and aging. Simultaneously, a modulation current component of the laser diode drive current is adjusted to maintain an extinction ratio of the laser diode output signal. The bias current and modulation current adjustments are based on the second order statistics of an average output power of the laser diode and a variance in the power output of the laser diode.

An object is to provide a wire grid polarizer with an excellent optical property, which enables to maintain the polarization extinction ratio high and level in the broadband wavelength region with a simple structure. A wire grid polarizer of the present invention comprises, a wire grid structural body in which a plurality of metal wires are formed and arranged at a certain period in a direction orthogonal to a longitudinal direction of the metal wires on a light-transmitting substrate, for transmitting only a specific linearly polarized light out of linearly polarized lights being orthogonal to each other, which make incident to the wire grid structural body, wherein a cross-sectional shape of the metal wire, which is orthogonal to the longitudinal direction, has a taper shape.

In a Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) utilizing a conventional downstream optical signal reusing method, there is an inventory problem that different optical transmitter types need to be provided for the operation, management, replacement, etc. of a system. A WDM-PON system according to the present invention, includes: a seed light (SL) unit generating a seed light whose wavelength intervals and center wavelengths are adjusted using at least one seed light source; an optical line terminal (OLT) receiving the wavelength-multiplexed seed light from the seed light unit, transmitting a downstream optical signal to a subscriber of the WDM-PON, and receiving a upstream optical signal from the subscriber; and an optical network unit (ONU) receiving the downstream optical signal from the OLT, flattening and modulating the downstream optical signal with upstream data so that the downstream optical signal is reused for carrying upstream data. It is possible to improve the quality and reliability of downstream transmission by sufficiently increasing an extinction ratio, and improve the quality and reliability of upstream transmission by sufficiently flattening an input downstream optical signal in a semiconductor optical amplifier.

A method for separating the orthogonal polarization components of an incident optical signal into two spatially separated output ports is described. The method comprises a Mach-Zehnder interferometer where one of the two branches has a section of waveguide that exhibits form-birefringence. This integrated optic Polarization Beam Splitter (PBS) is broadband, has high extinction ratio, and has characteristics that are tunable.

An amplified laser source for amplifying a laser projection that includes a diode laser source modulated by a pulse generator applying an alternate high and low voltages higher and lower than a threshold voltage for projecting a modulated optical signal. The laser source further includes a first erbium-doped fiber (EDF) for amplifying the modulated optical signal. The laser source further includes a set of Bragg gratings for receiving the modulated optical signal from the first EDF for reflecting a grating-specific pulse-distortion-reduced optical signal. The laser source further includes an electro-absorption (EA) modulator synchronized with the pulse generator for increasing an extinction ratio of the optical signals. The laser source further includes a second erbium doped fiber (EDF) for receiving and amplifying the optical signal from the EA modulator wherein the second erbium doped fiber (EDF) having a length of several meters and a diameter greater than or equal to thirty-five micrometers.