The new circular heterodyne interferometer with electro-optic modulation for measurement of the optical linear birefringence

We present a new circular heterodyne interferometer with electro-optic modulation for measurement of the optical linear birefringence. It enables the measurement of not only the phase retardation but also the principal angle. The measurement procedure is carried out in two steps. In the first step of measurements, we use the electro-optic modulated circular heterodyne interferometer and the phase-lock technique to precisely measure the principal axis angle. After rotating the analyzer in the setup, the phase retardation is determined also by the phase-lock technique. The compact configuration requires only a photodetector and two simple phase-lock extractions to determine the principal axis angle and the phase retardation. The validity of the proposed design is demonstrated by measurement of the principal axis angle and phase retardation of a quarter-wave plate sample. The root-mean-square resolutions for the principal axis angle and phase retardation are found to be 0.0396° and 0.0796°, respectively, with corresponding dynamic ranges of 0–180° and 0–180°.     

Linear birefringence parameters determination of a multi-order wave plate via phase detection at large oblique incidence angles

In order to characterize the linear birefringence parameters (LBPs) of a multi-order wave plate (MWP) including ordinary refractive index n_o, extraordinary refractive index n_e and the order number precisely, phase retardation measurement by means of large oblique incidence angle on the MWP has been proposed and demonstrated. However, the effects of spatial shifting and multiple reflections by the MWP depress the accuracy of the measurements significantly. Thus, we propose a retro-reflected geometry in a polarized heterodyne interferometer that can determine the LBPs of a MWP precisely. This method is not only able to reduce the spatial shifting effect but also avoids multiple reflections of the emerging beams. Experimentally, the oblique incidence angle in a range from 30° to 44° was scanned and the highest sensitivity ever for measurements of n_o and n_e for an uncoated MWP was obtained. The detection sensitivity for the refractive indices (n_o,n_e, n_o−n_e) of an uncoated MWP can be up to 10⁻⁶.     

Improved models of optical fiber birefringence—Part I

Current models of birefringence in optical fibers assume that the birefringence vector varies randomly either in direction with a fixed magnitude or simultaneously in both magnitude and direction. Here we propose and then investigate several models in which the stochastically varying amplitude is instead restricted to a limited range.     

Effect of dispersion of linear birefringence upon the sensitivity of an optical current sensor

The dispersion properties of the linear birefringence inside the glass current sensing head of a bulk glass optical current sensor and its effect upon the sensitivity of the sensor are theoretically analyzed and simulated with a computer. The investigation results show that the effect is small enough to be ignored, although it can certainly affect the scale factor of the system slightly. These results might be useful for the researchers and designers working in the optical current sensing techniques area.     

Drawing parameters optimization for birefringence reduction in optical fibers

The impact of the drawing process on the stress-induced birefringence in optical fiber is experimentally analyzed. By means of the photoelastic tomographic technique, residual internal stresses are measured in fiber samples drawn under different conditions of temperature, drawing tension and speed. From measured residual stress distributions, the stress-induced birefringence and beatlength are mathematically derived and compared, proving that an effective birefringence reduction can be obtained by a proper choice of drawing parameters.     

Measuring small wavelength differences by heterodyne interferometry and optical activity of chiral crystal

The optical activity of a chiral crystal and common-path heterodyne interferometry are used in a simple measurement technique that was developed to measure small wavelength differences. When circularly polarized heterodyne light passes through a chiral crystal, the plane of polarization rotates. The phase difference between the right- and left-circular lights is directly proportional to the angle of rotation. The rotation angle depends strongly on the wavelength. The phase difference can be accurately detected and substituted into specially derived equations to estimate wavelength variations. The feasibility of this method was demonstrated and the wavelength sensitivity was about 0.00812 nm. This method provides the advantages of a simple structure, ease of operations, a large wavelength measurement range and high sensitivity.     

Effects of linear birefringence inside sensing head upon bulk glass current sensors’ sensitivity

The effects of the linear birefringence inside a bulk glass current sensing element and the incident polarizing angle upon the performance of a bulk glass optical current sensor are derived and analyzed theoretically. The investigation results show that the linear birefringence will modify the scale factor of the system with a sample function; it can also affect the extent of the influence of the incident polarizing angle, at the same time. When the incident polarizing angle has some special values such as 0, 45, or 90, its effect on the system will be zero. These results might provide some useful reference to the researchers and designers of bulk glass optical current sensors.     

Novel polarization ellipticity angle modulation scheme for analog optical space communication

A novel polarization ellipticity angle modulation scheme is proposed and analyzed. The scheme shows linear modulation property and negligible phase noise. With this method, analog signal such as microwave sub-carrier can be directly encoded onto light carrier, simplifying the integration of traditional RF system and optical space communication system.     

The study of third harmonic demodulation in phase modulation optical heterodyne technique using optical resonator

With the technique of phase modulation optical heterodyne(PMOH), we detected the beat-frequency signal of the reflected wave from a F-P cavity. The frequency of the beat signal was three times of that of the modulation electric field, when the 3rd harmonic of the modulation electric field was used as the phase reference signal. The line shapes of the signal match those of the theoretical calculations, and the dispersion signal has good frequency-discrimination characteristic.     

The PMD of sinusoidally spun fibers in the presence of random birefringence perturbations

Although fiber spinning is known to reduce polarization mode dispersion (PMD) effects in optical fibers, relatively few studies have been performed of the dependence of the reduction factor on the strength of random birefringence fluctuations. In this paper, we apply a general mathematical model of random fiber birefringence to sinusoidally spun fibers. We find that while even in the presence of random birefringence perturbations the maximum reduction of PMD is still obtained when the phase matching condition is satisfied, the degree of PMD reduction and the probability distribution function of the DGD both vary with the random birefringence profiles.     

Alternative method of wavelength drift free dual-wavelength heterodyne interferometry for the absolute distance measurement

Based on the technique of dual-wavelength and principle of heterodyne interferometry, a modified method for measuring the absolute distance is proposed. Because two test lights suffer from the same influence of wavelength drift in the measurement setup, the minus effect coming from the wavelength drift can be offset. Therefore, the measurement accuracy can be significantly increased. The feasibility of this method was demonstrated with a measurement resolution of about 1.50 μm. This method provides the advantages of a simple optical setup, easy operation and rapid measurement.     

Optical-frequency dependent modal birefringence and polarization mode dispersion of birefringent single-mode optical fibers over a broadband optical wavelength range

Optical-frequency dependent polarization mode dispersion as well as modal birefringence of three kinds of specially designed hollow-induced birefringent single-mode fiber are measured over an optical frequency range between 345 and 410 THz by optical frequency-domain interferometry.     

Two-dimensional birefringence measurement system with a polarization modulator and a rotating analyzer

The measuring system of two-dimensional birefringence distribution with a polarization modulator and a rotating analyzer using a rotating analyzer method is presented. The system simply consists of a laser diode, two polarizers, two quarter wave plates and a CCD camera. Thanks to an imaging system, the mechanism to scan a sample is unnecessary and two-dimensional measurement is possible and easy. The birefringence of retardation and orientation of the optic axis can be determined by the azimuth angle of an elliptically polarized light passing through a sample. The azimuth angle is obtained by applying the phase shifting algorithm to measure the polarization properties; by improving the calculation algorithm, wide range measurement is accomplished. The measurement procedure and a number of results are described.     

A LabVIEW-based real-time measurement system for polarization detection and calibration

A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a computer running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments’ graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization.     

Photonic RF frequency measurement combining SSB-SC modulation and birefringence

A new technique to instantaneously measure microwave frequency and amplitude is presented and experimentally demonstrated. The architecture described is based on a single sideband modulation with suppressed carrier (SSB-SC) and the measurement of the Stokes parameters at the output of a birefringent medium. The results show errors below 50 MHz in the 59% of measurements carried out in a range from 1 to 11 GHz and an average power error of 0.34 dB. The technique shows the potential to increase the resolution and the range by increasing the differential time delay of the birefringent medium.     

Imaging quality analysis and evaluation of optical polarization imaging system with optical transfer matrix

An optical transfer matrix (OTM) is introduced and proposed to analyze the performance of optical polarization imaging systems. This 4 × 4 OTM describes the frequency transfer characteristics of the optical system for each Stokes parameter. It includes the transfer functions and the crosstalk functions. The transfer functions can be used to analyze the imaging quality of the system for each polarization component, while crosstalk functions indicate the polarization errors. We calculate the modulation transfer matrix as an example and numerically simulate the Stokes vector imaging for a polarization imaging system with a singlet and rotating polarization elements. The simulated imaging results show conformance with the analysis.     

Faraday mirror-typed optical current transformers and its theoretical analysis

A Faraday mirror-typed optical current transformer (OCT) design with turn-back optical paths is proposed to overcome the harmful effects of the linear birefringence inside bulk glass current sensing head, which can double the sensitivity and improve the state of polarization of the system output. The theoretical analysis of the working principle, the simulation of the polarization state of the output light beam and the comparison between it and the OCT with polarization preserving total reflection (PPTR) layers are presented. The results show that this design has a good suppressing effect on the degeneration of the polarization state of the output light, which has certain reference significance on the performance improvement of the present bulk glass OCT, and the development of practical OCTs.     

The application of a rotating-wave-plate stokes polarimeter for measurement of the optical rotation angle

An optical scheme based on Stokes-Mueller formalism and rotating-wave-plate Stokes polarimeter is successfully developed to measure the optical rotation angle in a chiral medium. The average relative error in the measured rotation angle of a half-wave plate is determined to be 1.16%. The average relative error in the measured rotation angles of glucose solutions with concentrations ranging from 0 to 1.2 g/dl is determined to be 3.78%. The correlation coefficient between the measured rotation angle and the glucose concentration is found to be 0.99950, while the standard deviation is just 0.00376°. From the inspection of measured rotation angle in the sol-gel materials containing C₁₇H₁₇ClO₆ with concentrations ranging from 0 to 0.0665 g/ml, the average relative error in the measured rotation angles is determined to be 3.63%. Consequently, the derived algorithm for measuring the rotation angle of a chiral medium is feasible, and the developed system is evaluated with a precision of 5.4% approximately in rotation angle measurement.     

A model to characterize the effect of cross phase modulation on polarization in an optical fiber transmission system

This paper presents a model that described the process of inter-influence between cross phase modulation (XPM) and polarization effects such as polarization mode dispersion (PMD) and polarization dependant loss (PDL) in an optical fiber communication system. Previous papers have discussed PMD-PDL and PMD-XPM effects in separate models, but in this work we developed a model that is capable of characterizing and evaluating PMD, PDL and XPM simultaneously. From the model, we found that PMD and PDL can be affected by XPM. The presence of XPM changed the vector directions of PMD and PDL in Stokes space.     

Control of modulation and soliton polarization instabilities in photonic crystal fibers with birefringence management

Photonic crystal fibers with composite linear birefringence, that is induced by both microstructure geometry and stress applying parts, permit the management of the wavelength dependence of both group and phase birefringence. In this work we investigate the novel nonlinear propagation phenomena that are enabled by birefringence management. Vector modulation instability is enhanced near the zero phase birefringence wavelength. Soliton polarization instability is controlled by Raman self-frequency shifting across the zero phase birefringence wavelength.