Article

All-fiber polarization interference filters based on 45°-tilted fiber gratings.

Photonics Research Group, Aston University, Birmingham, UK.
Optics Letters (Impact Factor: 3.18). 02/2012; 37(3):353-5. DOI: 10.1364/OL.37.000353
Source: PubMed

ABSTRACT We report all-fiber polarization interference filters, known as Lyot and Lyot-Őhman filters, based on alternative concatenation of UV-inscribed fiber gratings with structure tilted at 45° and polarization maintaining (PM) fiber cavities. Such filters generate comb-like transmission of linear polarization output. The free spectral range (FSR) of a single-stage (Lyot) filter is PM fiber cavity length dependent, as a 20 cm long cavity showed a 26.6 nm FSR while the 40 cm one exhibited a 14.8 nm FSR. Furthermore, we have theoretically and experimentally demonstrated all-fiber 2-stage and 3-stage Lyot-Őhman filters, giving more freedom in tailoring the transmission characteristics.

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    • "The Lyot filter is a type of polarization interference filter based on a combination of polarizers and waveplates in alternating sequence, from which a comb-like transmission spectrum could be generated [23], [24]. In our previous work, an all-fiber Lyot filter (AFLF) by sandwiching a segment of PM fiber between two 45° TFGs UV-inscribed in PM fiber has been reported [25]. The bandwidth and free spectra range (FSR) of a singlestage Lyot filter cannot be separately adjusted by changing the cavity length, because both of the bandwidth and FSR are inversely proportion to the length of the PM fiber, and the bandwidth of Lyot filter is half of the FSR [26]. "
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    ABSTRACT: We have demonstrated a switchable dual wavelength fiber ring laser with a high degree of polarization output by using an intracavity 3-stage all fiber Lyot filter. The filter is formed by concatenating four 45 $^{circ}$ tilted fiber gratings separated by polarization maintaining fibers with a length ratio of 1:2:4 (20, 40, and 80 cm), giving a compact integrated configuration with reduced bandwidth. Switchable dual wavelength or single wavelength output at 1533.5 and 1563.3 nm has been achieved. The output lasing is considerably stable owing to the in-phase mode-selecting function of the multistage Lyot filter, and has a very high degree of polarization higher than 99.9%.
    IEEE Photonics Technology Letters 06/2014; 26(11):1085-1088. DOI:10.1109/LPT.2014.2314865 · 2.18 Impact Factor
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    • "Moreover, we have inscribed 45° tilted fiber gratings (45°-TFGs) into PM fibers, which could be ideal for forming all-fiber Lyot filters. In our previous work, we have presented an all-fiber Lyot filter [17], i.e. an all-fiber polarization interference filter (AFPIF), which is based on two 45°-TFGs with a PM fiber cavity. "
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    ABSTRACT: We have theoretically and experimentally designed and demonstrated an all-fiber polarization interference filter (AFPIF), which is formed by a polarization-maintaining (PM) fiber cavity structure utilizing two 45° tilted fiber gratings (45°-TFGs) inscribed by UV laser on the PM fiber. Such a filter could generate modulated transmission of linear polarization status. It has been revealed that the modulation depth of the transmission depends on the coupling angle between the 45°-TFGs and the PM fiber cavity. When the two 45°-TFGs in PM fiber are oriented at 45° to the principal axis of the PM fiber cavity, the maximum modulation depth is achievable. Due to the thermal effect on birefringence of the PM fiber, the AFPIF can be tuned over a broad wavelength range just by simple thermal tuning of the cavity. The experiment results show that the temperature tuning s
    Journal of Lightwave Technology 01/2013; 31(1-1):94-98. DOI:10.1109/JLT.2012.2225022 · 2.86 Impact Factor
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    ABSTRACT: We demonstrate highly sensitive temperature and strain sensors based on an all-fiber Lyot filter structure, which is formed by concatenating two 45°-TFGs (tilted fiber gratings) with a PM fiber cavity. The experiment results show the all-fiber 45°-TFG Lyot filter has very high sensitivity to strain and temperature. The 45°-TFG Lyot filters of two different cavity lengths (18cm and 40 cm) have been evaluated for temperature sensing by heating a section of the cavity from 10°C to 50°C. The experiment results have shown remarkably high temperature sensitivities of 0.616nm/°C for 18cm and 0.31nm/°C for 40cm long cavity filter, respectively. The 18cm long cavity filter has been subjected to strain variations up to around 550μɛ and the filter has exhibited strain sensitivities of 0.02499nm/μɛ and 0.012nm/μɛ for two straining situations, where its cavity middle section of 18cm and 9cm were stretched, respectively.
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