Fiber Birefringence Measurement Research Articles

Distributed Fiber Birefringence Measurement Using Pulse-Compression \u03a6-OTDR

In this paper, a novel birefringence measurement method through the Rayleigh backscattered lightwave within single-mode fiber is proposed, using a single chirped-pulse with arbitrary state of polarization. Numerical analysis is carried out in detail, then pulse-compression phase-sensitive optical time domain reflectometry (PC-Φ-OTDR) with polarization-diverse coherent detection is employed to verify this method. A 2km spun single-mode fiber is tested with 8.6 cm spatial resolution, and the average birefringence of the fiber under test is measured as 0.234rad/m, which is consistent with previous literatures about single-mode fiber. Moreover, the relationship between the measured birefringence and the spatial resolution is also studied for the first time, and the results show that spatial resolution is crucial for fiber birefringence measurement.

Erratum to: Distributed Fiber Birefringence Measurement Using Pulse-Compression Φ-OTDR

The original article unfortunately contained a mistake. Figures 4 and 8 are not clear. The figures in original article and in corrected article are as follows.

Birefringence Measurement by Expandable Polarization Interference Method

In this article, an improved polarization interference method is proposed for fiber birefringence measurement. This method uses two different lengths of a birefringence fiber with their birefringent axes orthogonally coupled to compensate the phase difference and achieve the required pitch in interferogram for determining birefringence accurately. Experiments and analysis demonstrate that the method could offer improved accuracy and expanded range in birefringence measurement with relatively low spectral resolution systems.

Fiber birefringence measurement by an external applied strain method and a polarimetric fiber laser sensor.

In this work, a high-sensitivity and low-cost sensing scheme for measuring intrinsic and induced fiber birefringence change is reported based on a polarimetric fiber laser sensor interrogated by the beat frequency technique. The fiber birefringence measurement is achieved by an external applied strain method. A detailed theoretical analysis of the principle for fiber birefringence measurement is carried out. Two alternative equations are given for determining the change of fiber birefringence, which make it very convenient for users to choose different order beat signals. To verify the performance of the sensing system, the external applied strain-induced fiber birefringence change is measured experimentally. The experiment result shows that the fiber birefringence experiences a linear increase with the increase of applied strain. A strain response coefficient of 4.646×10-11/μϵ is obtained. Furthermore, the repeatability and stability performances of the polarimetric fiber laser sensor are also investigated.

Fiber Birefringence Measurement of Single-Mode Fiber by a Polarimetric Fiber Ring Laser

A novel and low-cost fiber birefringence measurement scheme is proposed and studied by a polarimetric fiber ring laser interrogated by the beat frequency technique. For the fiber ring laser, modes splitting occur between two orthogonal polarization modes because of intrinsic fiber birefringence. As a result, two types of beat frequency signals (i.e., longitudinal mode beat frequency and polarization mode beat frequency signals) are generated simultaneously. The principle of measurement of fiber birefringence by the fiber ring laser has been analyzed theoretically in detail. Two alternative expressions for fiber birefringence change are obtained, which is very convenient for users to choose different order longitudinal and polarization mode beat frequency signals. The variation of fiber birefringence caused by applied strain has been calculated in terms of beat frequency shift. To validate the proposed sensing system, the strain-induced fiber birefringence change in commercial Erbium-doped fiber is investigated and obtained by measuring frequency shift of two types of beat frequency signals. The experimental results show that the fiber birefringence experiences a linear decrease when the applied strain is increased. A strain response coefficient of –1.756 × 10–11/μe is obtained. The proposed sensing scheme has obvious advantages of simple structure, low cost, and high sensitivity and it will provide great convenience for measuring fiber birefringence for short-length single mode fiber.

Distributed birefringence measurement with beat period detection of homodyne Brillouin optical time-domain reflectometry

We report a distributed optical fiber birefringence measurement method based on homodyne Brillouin optical time-domain reflectometry (BOTDR). Unlike conventional BOTDR, which requires scanning of the local oscillator to get the Brillouin spectrum, instead we propose the beat period measurement of fast and slow components of the backscattered Brillouin signal in single-mode fibers using homodyne detection. The beat period is measured by detecting the envelope of the Brillouin beat signal, which gives the beat length at different fiber locations, so that birefringence can be calculated accordingly. The distributed birefringence of a 1.7 km SMF-28 and a 4.3 km large-effective-area fiber were measured with 0.6 m spatial resolution without frequency scanning of the Brillouin spectrum.

Fiber birefringence measurement based on a beat-frequency-interrogated multilongitudinal-mode distributed bragg reflector erbium-doped fiber laser

A novel fiber birefringence measurement scheme based on beat frequency interrogation of a multilongitudinal-mode distributed Bragg reflector erbium-doped fiber laser is presented and experimentally demonstrated. By analyzing the laser beat generation mechanism, an analytic expression describing fiber birefringence in terms of laser wavelength, laser beat frequency, and the fiber laser geometry has been obtained. Calculation of fiber birefringence based on the experimental observation of laser beat frequency shift indicates that the strain dependence of fiber birefringence turns out a perfect linear monotone decreasing relationship with a strain coefficient of ∼−2.2 × 10–11/μe, which is in good agreement with related reports. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:702–707, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26630

DBR‐fiber‐laser‐based active temperature sensor and its applications in the measurement of fiber birefringence

AbstractA fiber active temperature sensor based on single‐longitudinal‐mode distributed Bragg reflector (DBR) fiber laser is proposed and experimentally demonstrated. The dual‐polarization mode DBR fiber laser could be employed as a temperature sensor through beat frequency interrogation. The temperature sensitivities of this polarimetric sensor are experimentally compared both through frequency and wavelength interrogations. By calculating the fiber birefringence at different temperature, temperature dependence of fiber birefringence is also investigated. Theoretical analysis and experiment results indicate that the fiber birefringence would linearly decrease with the increase of temperature. Based on the frequency and wavelength interrogations, respectively, the fiber active sensor would provide an effective way to achieve simultaneous measurement of multi‐parameters. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 41–44, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24820

Measurement of beat length in short low-birefringence fibers using the fiber optical loop mirror

In this paper we provide a detailed analysis and investigation of a novel experimental method to measure the birefringence in short low-birefringence fibers. This method is based on the fiber’s twist in a fiber optical loop mirror. It allows simple birefringence measurement in fibers with beat length within the range of 0.4–100 m. The shortest fiber we were able to measure was 0.034 of beat length. Statistical error of measurements was less than 3%. To demonstrate the measurement technique we present experimental results for three optical fibers whose beat lengths were in the range from 1 to 19 m.

Measurements of beat length in short low-birefringence fibers

We describe a new experimental method of determining low birefringence in fibers, based on adjusting the fiber twist in a fiber-optic loop mirror. The method allows simple birefringence measurement in fibers with beat length within the range 0.05-100 m.

A Device for On-Line Measurement of Fiber Birefringence

A device for on-line measurements of fiber birefringence is described. The system consists of a double beam detection method coupled to an interference fringe device, allowing a quasi-simultaneous measurement of the diameter. A sensitive determination of birefringence is possible using this method. An example is given of an application to a fiber spun from a solution of cellulose in aqueous N-methylmorpholine-N-oxide.

Measurement of fiber birefringence by wavelength scanning: effect of dispersion

Scanning the wavelength in high-birefringence fibers inherently measures the group delay difference, and not the phase delay difference, between the two polarization modes. Dispersion of the birefringence will result in a 10-20% error in fiber beat lengths interpolated from such measurements, even if only stress birefringence is present. Geometrical dispersion can introduce even larger errors in some fibers.