Core-cladding mode coupling of tilted long period fiber gratings in dual-mode fibers
TL;DR: In this paper, the authors present a theoretical study on the mode coupling between core modes and cladding modes of the tilted long period fiber grating (TLPFG) in dual-mode fiber.
About: This article is published in Optics Communications.The article was published on 2017-06-15. It has received 10 citations till now. The article focuses on the topics: Cladding mode & Mode volume.
Citations
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TL;DR: This work design and fabricate several mode filters where graphene films of different widths and lengths are placed in different locations of polymer waveguides that can provide high mode extinction ratios that are insensitive to the operation wavelength.
Abstract: We propose spatial-mode filters based on embedding graphene films in optical waveguides. To demonstrate the effectiveness and the flexibility of this approach, we design and fabricate several mode filters where graphene films of different widths and lengths are placed in different locations of polymer waveguides. Our mode filters are easy to make and can provide high mode extinction ratios that are insensitive to the operation wavelength. Such mode filters could find applications in broadband mode-division-multiplexing transmission systems and other areas that involve mode selection or stripping.
38 citations
TL;DR: In this paper, a directional bending sensor based on thin-core fiber Bragg grating is proposed and demonstrated experimentally, which is inscribed by off-center technique and exposed by 193 nm ArF excimer laser through a phase mask.
15 citations
TL;DR: In this article, an improved piecewise discretization method for the finite-difference mode solver combined with coupling mode theory is presented to explore the general variation rule of mode characteristics and polarization-dependent resonances corresponding to polarized TE/TM0,m and HE/EHv,m modes of the graphene integrated Ex-TFG.
Abstract: The graphene integrated optical fiber devices show many excellent characteristics, especially their tunable optical properties. Here we investigate thoroughly the influence of the tuning property of the graphene on the resonance and sensing performance of the excessively tilted fiber grating (Ex-TFG) operating around the dispersion tuning point. An improved piecewise discretization method for the finite-difference mode solver combined with coupling mode theory is presented to explore the general variation rule of mode characteristics and polarization-dependent resonances corresponding to polarized TE/TM0,m and HE/EHv,m modes of the graphene integrated Ex-TFG. The results reveal that both p-polarized and s-polarized modes and their resonances are greatly influenced by the tunable graphene. On this basis, the sensitivity enhancement of the graphene coated Ex-TFG is explored in detail. It is shown that the sensing performance of both polarized cases can be greatly improved by tuning the chemical potential. In particular, the graphene induces a greater influence on both resonance wavelength and resonance strength of the s-polarized mode, but the p-polarized one has a higher sensitivity. We believe that these unique tuning properties make the graphene integrated Ex-TFG devices ideal for the telecommunication and sensing applications, such as tunable fiber modulators and biochemical sensors.
10 citations
TL;DR: The results show that the sensitivity can be optimized based on the combined effects of the intermodal separation, initial wavelength separation, and the variation in the phase matching curve.
Abstract: In this paper, we report a sensitive refractive index sensor based on the titanium dioxide (TiO $ _2$ ) film coated excessively tilted fiber grating (Ex-TFG) operating around the dispersion tuning point. The effects of the TiO $ _2$ film on the cladding mode field, transmission, and sensing characteristics of the Ex-TFG are outlined. It is found that the TiO $ _2$ film induces a two-step mode transition process for both TE/TM $ _{0,l}$ and HE/EH $ _{v,l}$ ( $ v=1,2,\ldots$ ) cladding modes. During the first transition, the same optimized film thickness can be obtained for TE $ _{0,l}$ , HE $ _{1,l}$ , and EH $ _{2,l-1}$ cladding modes. The results show that the sensitivity can be optimized based on the combined effects of the intermodal separation, initial wavelength separation, and the variation in the phase matching curve (i.e., $ \partial \Lambda / \partial \lambda$ ). The improved sensitivities are up to $ 32261.2\;\text{nm}/\text{RIU}$ and $ 23183.3\;\text{nm}/\text{RIU}$ by tracking dual resonance band corresponding to the s-polarized TE $ _{0,10}$ and p-polarized EH $ _{2,9}$ cladding modes, respectively, in the low refractive index region. For the single resonance corresponding to the s-polarized HE $ _{1,9}$ cladding mode, the sensitivity as high as $ 25860.0\;\text{nm}/\text{RIU}$ is achieved. The sensitivity is significantly enhanced by a factor of $ 13.2 \sim 18.1$ and $ 3.7 \sim 5.2$ times as compared with the uncoated Ex-TFG and classical TiO $ _2$ film coated long period fiber grating with reduced fiber diameter, respectively. The sensitivity can be further improved, which makes the film coated Ex-TFG very attractive for the refractive index sensing.
8 citations
Cites background or methods or result from "Core-cladding mode coupling of tilt..."
...[20], [21], [33]), which will be analyzed in detail in Section IV....
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...Compared with the uncoated Ex-TFG that has degenerate spectrum [20], [21], [33], the TiO2 overlay breaks this degeneracy associated with the resonance of TE0,l and EH2,l−1 cladding modes....
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...fiber and few mode fiber respectively [20], [21]....
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...ing characteristics of the Ex-TFG utilizing the CCMT that has been proved to be a powerful tool for the simulation of fiber gratings [19]–[21]....
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...This has been also verified by other researchers [20], [21], [32]....
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TL;DR: An excessively tilted LPFG-assisted surface plasmon polaritons sensor with ultrahigh sensitivity and a transition point corresponding to the phase matching curve of the SPP mode is obtained are confirmed and can be used to predict the optimized grating period.
Abstract: An excessively tilted LPFG-assisted surface plasmon polaritons sensor (Ex-TLPFG assisted SPP sensor) with ultrahigh sensitivity is proposed and numerically investigated using the finite-element-method-based full-vector complex coupled mode theory. We show that the SPP mode is transited (or excited) gradually from both the p-polarized TM $_{0,j}$ and EH $_{v,j}$ ( $v\geq 1$ ) modes, and hence, the proposed SPP sensor can be tuned to achieve strong resonance of either the degenerate TM $_{0,j}$ and EH $_{2,j}$ modes or EH $_{1,j}$ mode to optimize the sensitivity for analyte refractive index sensing. The results confirm that a transition point corresponding to the phase matching curve of the SPP mode is obtained, which can be used to predict the optimized grating period. By this approach, ultrasensitive SPP refractometric sensor can be obtained and the sensitivity can be further improved through a simple method: reducing the fiber cladding combined with an optimized grating period. We demonstrate that a giant sensitivity as high as $10100\,\text{nm}/\text{RIU}$ is achieved for the degenerate TM $_{0,32}$ and EH $_{2,32}$ modes (or $7400\,\text{nm/RIU}$ for the EH $_{1,32}$ mode). These appealing characteristics make the proposed Ex-TLPFG-assisted SPP sensor ideal for biochemical analyte sensing applications.
5 citations
Cites background from "Core-cladding mode coupling of tilt..."
...However, LPFGs can also couple the guided core mode to the higher order degenerate TE/TM0,j and HE/EHv,j (v ≥ 2) cladding modes, especially for the excessively tilted Ex-LPFGs (Ex-TLPFGs) as well as the non-uniform perturbation LPFGs [11], [21]....
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References
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TL;DR: In this paper, a detailed theoretical treatment of the effects of grating tilt on the spectral characteristics of a tilted optical-fiber phase grating is presented, compared with experimentally measured spectra of strong gratings.
Abstract: A detailed theoretical treatment is presented of bound-mode to bound-mode Bragg reflection and bound-mode to radiation-mode coupling loss in a tilted optical-fiber phase grating. Numerical predictions of the effects of grating tilt on the spectral characteristics of such a grating are calculated. These predictions are compared with experimentally measured spectra of strong gratings written by ultraviolet irradiation of deuterium-sensitized fiber with grating tilt angles ranging from 0° to 15°. Good agreement is obtained between the theoretical predictions and the experimental results.
428 citations
06 Mar 2011
TL;DR: In this article, the authors demonstrate the transmission of 6 independent, spatially and polarization multiplexed 28-Gb/s QPSK signals over 10 km of three-mode fiber using mode-selective excitation and full coherent 6 × 6 MIMO processing.
Abstract: We demonstrate the transmission of 6 independent, spatially- and polarization multiplexed 28-Gb/s QPSK signals over 10 km of three-mode fiber using mode-selective excitation and full coherent 6 × 6 MIMO processing.
277 citations
06 Mar 2011
TL;DR: In this paper, two 100Gb/s PDMQPSK data streams over two different modes of a 40km-long prototype few-mode fiber were transmitted with an LCOS-based mode multiplexer/demultiplexer and 4×4 MIMO algorithm in a coherent receiver.
Abstract: We transmit two 100Gb/s PDM-QPSK data streams over two different modes of a 40km-long prototype few-mode fiber. Our experiment is performed with an LCOS-based mode multiplexer/demultiplexer and 4×4 MIMO algorithm in a coherent receiver.
164 citations
TL;DR: It is shown that strong coupling between an LP(01) core mode and the exact (1m) cladding modes occurs in a transmissive tilted grating for nearly any tilt angle except angles close to 90 degrees, whereas the LP-to-lm cladding mode coupling is appreciable only for tilt angles just below 90 degrees.
Abstract: Whereas core-mode reflection and core-mode-to-radiation-mode coupling in tilted fiber Bragg gratings is well understood, as is coupling between a core mode and higher-order core and cladding modes in untilted gratings, here we analyze in detail the coupling among core modes and cladding modes in reflective and transmissive tilted fiber gratings. We show that strong coupling between an LP(01) core mode and the exact (1m) cladding modes occurs in a transmissive tilted grating for nearly any tilt angle except angles close to 90 degrees, whereas the LP(01)-to-(lm) cladding mode coupling (l not equal 1) is appreciable only for tilt angles just below 90 degrees (approximately 88 degrees). In a reflective grating, strong coupling between the LP(01) core mode and the exact (1m) cladding modes occurs only for angles less than approximately 5 degrees, whereas coupling to (1m) cladding modes for m > 1 occurs only for angles greater than approximately 5 degrees. Coupling among bound core modes exhibits a similar behavior, except that in general the coupling is stronger. Experimentally we show coupling to both higher-order bound core modes and cladding modes in a transmissive tilted grating at visible and near-infrared wavelengths.
161 citations
TL;DR: In this paper, a simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed.
135 citations