117 results about "Relative intensity noise" patented technology

A system and method is provided which suppresses relative intensity noise in a fiber optic gyroscope by taking advantage of the frequency response of erbium fiber. In operation, the gain provided by the erbium fiber is added to the gain of the other components in the feedback loop to provide for stable loop performance up to about 250 kHz. The frequency response of the erbium fiber of about 3 kHz also provides a 6 db per octave roll-off, which, when used in a negative feedback control loop for controlling the current flowing to the gyroscope light source, allows for a relative intensity noise control loop with a bandwidth much greater than 3 kHz; this may be used in high performance gyroscope applications.

The invention discloses a Brillouin optical time domain analyzing and sensing system based on ultra-long annular laser pumping. The Brillouin optical time domain analyzing and sensing system based on the ultra-long annular laser pumping comprises first-order raman pump light (16) with the wavelength of 13 xxnm, a wavelength division multiplexer WDM pair (17) and a sensor fiber (18), wherein the wavelength division multiplexer and the sensor fiber form an ultra-long distance annular laser resonant cavity, the first-order raman pump light is fed back by the annular laser resonant cavity to generate lasing light with the wavelength of 14 XXnm. The lasing light with the wavelength of 14 XXnm performs second-order raman amplification on probe light with wavelength of 15 XXnm and Brillouin pumping. In comparison with a Brillouin sensing system based on linear cavity amplification, sensing signals are distributed more smoothly along the optical fiber, and the consistency of sensing quality in the whole process is remarkably improved; noise transfer of pumping-signal relative strength can be effectively suppressed, and temperature, spatial resolution of strain detection and measurement accuracy can be substantially improved; due to the fact that an extra second-order pump light source does not need to be added, substantial stretching of the sensing distance is obtained with low cost, and the Brillouin optical time domain analyzing and sensing system based on the ultra-long annular laser pumping has certain practicability.

A laser transmitter with a feedback control loop for minimizing noise. The novel laser transmitter includes a laser, an external reflector adapted to form an extended cavity to the laser, and a feedback control loop adapted to detect noise in the laser and in accordance therewith, adjust the optical phase of the extended cavity such that the noise is at a desired level. The optical phase of the extended cavity is adjusted by adjusting an operating parameter of the laser, such as its bias current. In an illustrative embodiment, the feedback control loop is adapted to compute the rate of change of the noise with respect to bias current and in accordance therewith, adjust the bias current of the laser such that relative intensity noise and interferometric intermodulation distortion are simultaneously minimized.

A semiconductor laser comprises an electrically isolated active section and at least one noise reducing section and operates on a ground state transition of a quantum dot array having inhomogeneous broadening greater than 10 nm. The laser preferably emits more than 10 optical modes such that a total relative intensity noise of each optical mode is less than 0.2% in the 0.001 GHz to 10 GHz range. The spectral power density is preferably higher than 2 mW/nm. An optical transmission system and a method of operating a quantum dot laser with low relative intensity noise of each optical mode are also disclosed.

An optical coherence analysis system uses a laser swept source that is constrained to operate in a mode locked condition using regenerative mode-locking This is accomplished by synchronously changing the laser cavity's net gain and/or phase based on time varying intensity of the swept optical signal generated by the laser. This produces a stable pulsation behavior, which is associated with smooth tuning (low optical frequency reference clock jitter) and low relative intensity noise (RIN).

A method and apparatus for producing single mode random fiber ring laser by inducing random distributed feedback in a short section of the fiber ring to thereby enable single mode lasing while reducing frequency jitter and relative intensity noise. The random distributed feedback maybe achieved through deep refractive index modulation at a series of randomly distributed laser-irradiated points inscribed along the length of the induced random distributed feedback fiber. The laser-processed random distributed feedback fiber maybe incorporated into the fiber ring in conjunction with a variable optical attenuator and band pass optical filter for enhancing the single mode operation.

Method and apparatus are provided for a silicon substrate optical system for use in an interferometric fiber optic gyroscope (IFOG). A silicon substrate of the silicon substrate optical system is etched to receive optical components, including an input optical fiber, a pump source, a wavelength division multiplier, an isolator, a polarizing isolator, a beam splitting device, a PM tap coupler, a relative intensity noise (RIN) photodiode, a system photodiode, and an output optical fiber. The optical components are mounted on a silicon substrate to reduce the size and cost of the IFOG and increase reliability.

Effective relative intensity noise (RIN) subtraction systems and methods for improving ARW performance of a depolarized gyros. This invention taps the RIN detector light in the sensing loop, after the light transmits through the depolarizer and the coil but before it combines with the counter propagating lightwave. The tapped RIN lightwaves are polarized with pass-axis orientated in the same direction as that of the IOC, so that the RIN detector receives lightwaves with spectrum substantially identical to that of the rate detector, leading to more effective RIN subtraction.

A laser module includes a semiconductor laser element and a feedback optical component forming an external cavity with the semiconductor laser element. Even if a ratio of a current threshold of the laser module changing according to a polarized state of returned light from the feedback optical component to a current threshold of the semiconductor laser element is in an arbitrary range within a predetermined range, a total value of a relative intensity noise occurring between a first frequency determined according to a cavity length of the external cavity and at least equal to or more than a frequency band of using a laser light and a second frequency calculated by multiplying the first frequency by a predetermined number is equal to or more than −40 dB.

The invention provides a light source relative intensity noise suppression device using a double polarization maintaining coupler, belonging to the technical field of fiber optic gyroscope. The lightsource relative intensity noise suppression device using the double polarization maintaining coupler comprises an ASE light source, a 2x2 polarization maintaining coupler, a Y-waveguide integrated optical device, a polarization maintaining fiber ring, a 95:5 polarization maintaining coupler and a detector. A 5% branch of the 95:5 polarization maintaining coupler and one branch of the 2x2 polarization maintaining coupler are welded together by a method of 90 degree melting point. The ASE light source is split into two paths of light by passing through the 2x2 polarization maintaining coupler; one path of the light is a signal light, which is divided into two paths after passing through the Y-waveguide integrated optical device and then enters into the polarization maintaining fiber ring forinterference, and the interference light is input to the 95:5 polarization maintaining coupler through the 2x2 polarization maintaining coupler; and the other path of the light is a reference light,which is input to the 95:5 polarization maintaining coupler after the 90 degree melting point. The polarization states of the interference light and the reference light are perpendicular; therefore, no interference occurs when the light is combined, and the optical power is superimposed; so that the suppression of relative intensity noise is realized; moreover, the invention has a simple structureand is easy to implement.

Apparatus for the generation of ultra-low noise light comprising: a laser generating light at a central frequency and having a frequency dependent relative intensity noise spectrum; and an optical filter having a substantially conjugate symmetric transfer function; wherein the center frequency of the light generated by the laser is substantially aligned with the peak transmission frequency of the filter; and wherein the transmission function of the filter is chosen, and the frequency dependent relative intensity noise spectrum of the laser is adjusted, to reduce the resulting relative intensity noise of the light at the output of the filter over a range of frequencies by causing the relative intensity noise spectrum of the laser to occur at frequencies for which the filter has substantial loss.

The invention relates to a high-precision optical fiber gyroscope, and belongs to the technical fields of optical fiber sensing and inertial navigation. The high-precision optical fiber gyroscope is characterized in that a circuit board comprises a main board and a light source board; a loop assembly comprises an optical fiber ring base, a polarization-maintaining optical fiber ring, a erbium-doped fiber press plate, a wavelength division multiplexer, an isolator, a reflective mirror, a wave guide plate, a coupler, a temperature sensor and a Y-shaped wave guide; the outside wall of the opticalfiber ring base is provided with an annular installation groove for accommodating the polarization-maintaining optical fiber ring; the base is positioned between an upper casing and a lower casing, and is used for separating a gyroscope body into an upper part and a lower part; the circuit board is positioned at the upper part of the gyroscope body, and the loop assembly is positioned at the lower part of the gyroscope body. The high-precision optical fiber gyroscope has the advantages that a heating device and a sensitive optical fiber ring are physically isolated by the base, so as to reduce the heat radiation interference of a transmission device to the light path part; a magnetic shielding technique is adopted for the optical fiber loop, so as to shield the geomagnetic interference and circuit electronic interference; a light source with stable wide bandwidth and high power of 1550 nm is built, so that the output wavelength is not sensitive to the temperature, and the relative intensity noise of the light source is inhibited.

The invention discloses a device and method for measuring relative intensity noise of a laser. According to the method for measuring the relative intensity noise of the laser, the principle that after a single frequency point electric signal passes through a microwave photon link, a phase-noise index is correspondingly deteriorated is adopted and the relative intensity noise of the laser in the link is calculated through the change quantity of phase noise. The basic structure of the device for measuring the relative intensity noise of the laser comprises a single frequency point signal resource, a microwave photon link, an optical power meter and a phase-noise detector, wherein the microwave photon link is mainly composed of the laser, an electro-optical modulator, an optical coupler and a photoelectric defector. Compared with a traditional measuring method, the method for measuring the relative intensity noise of the laser has the advantages that the measuring process is conducted on the high-frequency end of an electricity domain, influence caused by various environment noises near the direct current end is avoided, the measuring accuracy is improved, the output power of the laser to be detected does not need to be considered according to the scheme, and the limitation, caused by optical output power, of a measuring system in the traditional measuring method is overcome.

The invention provides a FRM-based light source relative intensity noise cancellation structure, and belongs to the technical field of fiber optic gyros. The structure of the invention comprises an ASE light source, a single polarization 2*2 polarization-maintaining coupler, a Faraday rotating mirror (FRM), a Y-waveguide integrated optical device, a polarization-maintaining fiber loop, and a detector, wherein the light from the ASE light source becomes a polarized light passing through the 2*2 polarization-maintaining coupler, and is then divided into two beams, of which one is used as a signal light and the other one a as reference light; the signal light is divided into two beams through the Y-waveguide integrated optical device into the fiber loop for interference, the reference light passes through the FRM such that the polarization state is rotated by 90 degrees and reflected, and the reference light and the reflected light combine to enter the detector. The reference light and the interference light of the invention have a certain time difference, and the polarization states are perpendicular to each other with no interference occurring when the lights are combined, so that the optical power is increased, and the suppression of the relative intensity noise is completed.

Amulti-wavelength generating apparatus generates a wavelength division multiplexing (WDM) signal by modulating light with a single central frequency and an electric signal having a particular pulse repetition frequency. The resulting optical spectrum configuration is conntrollable so that a Relative Intensity Noise (RIN) or Signal to Noise Ratio (SNR) requirement may be achieved. A modulated or pulsed light source in used to obtain a descrete spectrum with particular mode spacing, which is then modulated to permit dynamic power control for specific modes of the discrete spectrum.

An optical coherence analysis system uses a laser swept source that is constrained to operate in a mode locked condition. This is accomplished by synchronously changing the laser cavity's gain and/or phase based on the round trip travel time of light in the cavity. Many high-speed wavelength swept laser sources emit pulses synchronized with the round trip time of the cavity as part of a nonlinear optical frequency red shifting process. Stable pulsation is associated with smooth tuning and low relative intensity noise. Addition of mode-locking methods to this class of lasers can control and stabilize these lasers to a low clock jitter and RIN state, and in specific cases allow long-to-short wavelength tuning in addition to the usual short-to-long (red shifting). The laser may comprise a SOA (410), a tunable Fabry-Perot-Filter (412) as one reflector and an Output coupler (405) in an optical fiber (406) to adjust the cavity length.

A system for determining a level of angle random walk (ARW) associated with a fiber optic gyroscope (FOG) includes first and second photodiodes. The first photodiode is configured to receive a first light signal from a light source associated with the FOG. The second photodiode is configured to receive a second light signal from a fiber optic coil associated with the FOG. First and second analog-to-digital converters (ADCs) are operable to respectively convert the first and second light signals into corresponding respective first and second digital signals. A digital relative-intensity-noise (RIN) subtraction element is configured to receive the first and second digital signals and output a third signal based on the first and second digital signals. An electronic device is configured to determine a first noise level associated with the third signal, and determine the ARW level from the first noise level.

The invention discloses a photoelectric conversion module relative intensity noise (RIN) test device and test method, comprising employing an electric signal supply module to supply high speed signals for a photoelectric conversion module to be detected; utilizing a reflection module to form reflected light to interfere the photoelectric conversion module to be detected; utilizing an optical power calculation and display module to control reflected light signal attenuation according to the power difference standard between the emission light and the reflected light of the photoelectric conversion module to be detected; providing required reflection interference light signals for the photoelectric conversion module to be detected; utilizing an optical eye pattern display module to display the emission light eye pattern of the photoelectric conversion module after reflected light interference; and selecting a worst value among the jitter values of the eye patterns in the eye pattern display module as a sampling eye pattern to calculate an RIN index. The test device and test method solve the problems of inconvenient wiring and complex data analysis of a current photoelectric conversion module RIN test method, thereby conveniently and visually obtaining the RIN index of the photoelectric conversion module to be detected.

The invention discloses an optical fiber communication transmission system and method applied to multi-wavelength pumping high-order bidirectional Raman amplification, which are applied to an ultra-long span optical fiber communication system and a common optical fiber communication system, can reduce one pump light in a multi-wavelength pumped bidirectional high-order Raman amplifier, and solve the problems of high relative intensity noise and low gain efficiency in a current multi-wavelength pumped high-order Raman amplification process and meanwhile reduce the system cost. A pump light closest to a signal light wavelength is reduced on a forward high-order Raman amplifier; and a reflection-type fiber grating filter is inserted respectively at an output end of the forward high-order Raman amplifier and an input end of a backward high-order Raman amplifier, and the central wavelength of the fiber grating is the wavelength of the pump light that has been reduced. The method of the invention can reduce the number of pump lights of the high-order Raman amplifier and reduce cost, and at the same time, reduce the relative intensity noise of the high-order Raman amplifier, greatly improve the backward gain and forward gain efficiency of the high-order Raman amplifier, and extend the transmission distance of a bidirectional high-order Raman fiber communication system.