Polarisation state optimisation in observing Brillouin scattering signal in polymer optical fibres

2014

Electron. lett.

Self Cite

It has been experimentally shown that by utilising the Fresnel-reflected light as the reference light, Brillouin signals in polymer optical fibres (POFs) can be observed with a higher signal-to-noise ratio (SNR) than those measured with standard self-heterodyne detection. This method is basically the same in setup as direct detection, leading to an additional advantage of system simplicity. Moreover, it has been demonstrated that the Brillouin signal in a 1 cm-long POF can be observed with a moderate SNR using this technique, indicating a potential feasibility of POF-based distributed Brillouin measurement with a millimetre-order spatial resolution.

supporting

confidence: 89%

Fresnel‐assisted self‐heterodyne detection for Brillouin gain spectrum characterisation in polymer optical fibres

Mizuno

2014

Electron. lett.

Self Cite

“…The solid circles and hollow squares indicate the measured points with increasing and decreasing temperature, respectively. PFGI-POFs, may contribute to the mitigation of the Brillouin signal deterioration caused by Rayleigh noise [27]. Although the absolute value of the temperature coefficient in PPFS-POFs was slightly lower than that in PFGIPOFs, it was still approximately 3.3 times as large as that in a standard silica SMF.…”

Section: Resultsmentioning

confidence: 91%

Dependence of Brillouin frequency shift on temperature in poly(pentafluorostyrene)-based polymer optical fibers estimated by acoustic velocity measurement

Minakawa

Koike

IEICE Electron. Express

et al. 2014

Poly(pentafluorostyrene) (PPFS), which can be easily synthesized and has a low optical loss window at 850 nm, is a promising alternative for a costly perfluorinated polymer as a base material of polymer optical fibers (POFs). To investigate the potential of a PPFS-POF as a Brillouin-based temperature sensing fiber, the Brillouin frequency shift and its temperature dependence of PPFS were measured using an ultrasonic pulse-echo technique. The temperature coefficient, which determines the sensitivity of the temperature sensing, was approximately !7.1 MHz/K independently of the molecular weight and was nearly identical to that in perfluorinated POFs.

“…These three behaviors are independent of one another; for instance, a minimized interference pattern generally does not lead to a maximized Brillouin peak power. Therefore, by suppressing the influence of the interference pattern using one of the aforementioned methods, the polarization state can be adjusted solely to maximize the Brillouin peak power in silica SMFs or to minimize the Rayleigh noise in the case of POFs [54]. This interference pattern suppression results in BGS and BFS detection with the highest SN ratio, even when the polarization state cannot be arbitrarily adjusted.…”

Section: Discussionmentioning

confidence: 99%

“…The polarization state adjustment was not influenced by the interference pattern. However, to maximize the SN ratio of the BGS measurement (i.e., the difference between the Brillouin peak power and the noise floor), the suppression of the Rayleigh noise (tail of the Rayleigh-scattered light spectrum) is more important than the enhancement of Brillouin peak power [54]. Note that Rayleigh noise is a phenomenon unique to POFs with a low BFS.…”

Section: Brillouin Measurement In Pofsmentioning

confidence: 99%

Fiber-Optic Interferometry Using Narrowband Light Source and Electrical Spectrum Analyzer: Influence on Brillouin Measurement

Mizuno

2014

J. Lightwave Technol.

We observe an interference pattern using a simple fiber-optic interferometer consisting of an electrical spectrum analyzer and a narrowband light source, which is commonly employed for observing the Brillouin gain spectrum. This interference pattern expands well beyond the frequency range corresponding to the Brillouin frequency shift in silica fibers (ß11 GHz at 1.55 μm). Using both silica single-mode and polymer optical sensing fibers, we then experimentally prove that the distinctive noise in a selfheterodyne-based Brillouin measurement with an unoptimized polarization state originates from the interference between the reference light and the Fresnel-reflected light. This noise can be almost completely suppressed by employing a delay line that is longer than the coherence length of the light source and by artificially applying a high loss near the open end of the sensing fiber. Index Terms-Brillouinscattering, fiber-optic interferometry, nonlinear optics, polymer optical fiber. I. INTRODUCTION S UBSTANTIAL efforts have been directed toward the study of Brillouin scattering in optical fibers [1] in the last 40 years, and a number of related applications have been developed, including lasing [1], microwave signal processing [2], core alignment [3], optical memory [4], slow light generation [5], and distributed strain and temperature sensing [6]-[10]. To improve the performance of these applications, Brillouin scattering properties have been investigated not only in standard silica glass fibers [11], [12] but also in various specialty fibers, such as tellurite fibers [13], [14], bismuth-oxide fibers [14], chalcogenide fibers [15], photonic crystal fibers [16], and fibers doped with rare-earth ions (erbium, thulium, etc.) [17], [18]. Each fiber type has its own distinctive features; for instance, the Brillouin scattering power in tellurite and chalcogenide fibers is far higher than that in other fibers, whereas the Brillouin scattering power in erbium-doped fibers at 1.55 μm can be tuned by controlling the 980-nm pump power. However, all of these glass fibers are fragile and require careful handling; in sensing Manuscript