Showing papers on "Photonic-crystal fiber published in 2014"
TL;DR: A novel hollow core fiber design based on nested and non-touching antiresonant tube elements arranged around a central core is proposed and it is demonstrated through numerical simulations that such a design can achieve considerably lower loss than other state-of-the-art hollow fibers.
Abstract: We propose a novel hollow core fiber design based on nested and non-touching antiresonant tube elements arranged around a central core. We demonstrate through numerical simulations that such a design can achieve considerably lower loss than other state-of-the-art hollow fibers. By adding additional pairs of coherently reflecting surfaces without introducing nodes, the Hollow Core Nested Antiresonant Nodeless Fiber (HC-NANF) can achieve values of confinement loss similar or lower than that of its already low surface scattering loss, while maintaining multiple and octave-wide antiresonant windows of operation. As a result, the HC-NANF can in principle reach a total value of loss – including leakage, surface scattering and bend contributions – that is lower than that of conventional solid fibers. Besides, through resonant out-coupling of high order modes they can be made to behave as effectively single mode fibers.
432 citations
TL;DR: A 3x1 fiber-based photonic lantern spatial-multiplexer with mode-selectivity greater than 6 dB and transmission loss of less than 0.3 dB is demonstrated, which are to the authors' knowledge the lowest insertion and mode-dependent loss devices.
Abstract: We demonstrate a 3x1 fiber-based photonic lantern spatial-multiplexer with mode-selectivity greater than 6 dB and transmission loss of less than 0.3 dB. The total insertion loss of the mode-selective multiplexers when coupled to a graded-index few-mode fiber was < 2 dB. These mode multiplexers showed mode-dependent loss below 0.5 dB. To our knowledge these are the lowest insertion and mode-dependent loss devices, which are also fully compatible with conventional few-mode fiber technology and broadband operation.
347 citations
TL;DR: In this paper, a few-layer Molybdenum sulfide (MoS2) polymer composite is used as broadband saturable absorber (SA) for Q-switching.
Abstract: We propose and demonstrate 1, 1.5, and 2 μm passively Q-switched fiber lasers by exploiting a few-layer Molybdenum sulfide (MoS2) polymer composite as broadband saturable absorber (SA), respectively. The few-layer MoS2 nanosheets are prepared by the liquid-phase exfoliation method, and are composited with polyvinyl alcohol (PVA). The PVA-MoS2 film is sandwiched between two fiber ferrules to form the fiber-compatible SA. The few-layer MoS2 not only shows good transparency from ultraviolet to mid-infrared spectral region, but also possesses the nonlinear saturable absorption. The modulation depth and saturation optical intensity of the PVA-MoS2 film are measured to be 1.6% and 13 MW/cm2 at 1566 nm by the balanced twin-detector technique, respectively. By further inserting the filmy PVA-MoS2 SA into the cavities of Yb-, Er- and Tm-doped fiber lasers, we achieve stable Q-switching operations at 1.06, 1.56, and 2.03 μm, respectively. The output characteristics of the Q-switched pulses at the three wavelengths have been investigated, respectively. The MoS2-based Q-switching enables the large pulse energy of ∼1 μJ with a pulse width of 1.76 μs. This is, to the best of our knowledge, the first demonstration of MoS2-based Q-switched fiber lasers in a wide wavelength range (from 1 to 2 μm). Our results experimentally confirm that the new-type 2-D material, few-layer MoS2, is a promising broadband SA to Q-switch fiber lasers covering all major wavelengths from near- to mid-infrared region.
320 citations
08 Jun 2014
TL;DR: In this paper, a review of recent advances in the fundamental understanding and active control of quantum fluids of light in nonlinear optical media is presented. And perspectives in the direction of strongly correlated photon systems are outlined.
Abstract: This tutorial reviews recent advances in the fundamental understanding and active control of quantum fluids of light in nonlinear optical media. Perspectives in the direction of strongly correlated photon systems are outlined.
282 citations
TL;DR: In this article, a graphene-based photonic crystal fiber (PCF) sensor based on surface plasmon resonance was proposed, which showed high amplitude sensitivity of 860 RIU-1 and has a resolution as high as 4×10-5 RIU.
Abstract: We propose a graphene-based photonic crystal fiber (PCF) sensor based on surface plasmon resonance. Graphene helps in prevention of oxidation of the silver layer used as a plasmonic active metal. The birefringent nature of the structure allows one component of the core guided mode to be more sensitive. Further, this structure does not need filling of the voids. The structural parameter of PCF and metal thickness has been optimized. The proposed sensor shows high amplitude sensitivity of 860 RIU-1 and has a resolution as high as 4×10-5 RIU. This reported performance is higher than bimetallic (gold on silver) configuration.
227 citations
TL;DR: In this paper, the authors demonstrate the use of a new saturable absorber material, antimony telluride (Sb2Te3), for efficient mode-locking of an Erbium-doped fiber laser.
Abstract: We demonstrate the usage of a new saturable absorber material – antimony telluride (Sb2Te3) for efficient mode-locking of an Erbium-doped fiber laser. The Sb2Te3 layers were obtained by mechanical exfoliation and transferred onto the fiber connector tip. The all-fiber laser was capable of generating optical solitons with the full width at half maximum of 1.8 nm centered at 1558.6 nm, with 4.75 MHz repetition rate. The pulse energy of the generated 1.8 ps pulses was at the level of 105 pJ.
224 citations
TL;DR: In this paper, the current state of the art in infrared Bi-doped fiber laser research is reviewed and the relevant fiber glass compositions and fiber technologies are introduced, as well as the energy level schemes of these centers.
Abstract: The current state of the art in infrared Bi-doped fiber laser research is reviewed. The relevant fiber glass compositions and fiber technologies are introduced. Lasers operating on transitions ranging from 1.15 to 1.55 μm occurring in the bismuth active centers and their energy level schemes are discussed on the basis of the spectroscopic properties of these centers. Continuous-wave fundamental-mode power levels ranging from a few mW near 1.55 μm up to 16 W near 1.16 μm and 22 W near 1.46 μm have been demonstrated in recent years.
179 citations
TL;DR: In this paper, the authors proposed a biosensor based on photonic crystal fiber made of polymethyl methacrylate using surface plasmon resonance, which consists of a layer of air holes as cladding and a central hole for phase matching between PLASM mode and core guided mode.
Abstract: We propose a biosensor based on photonic crystal fiber made of polymethyl methacrylate using surface plasmon resonance. The proposed sensor consists of a layer of air holes as cladding and a central hole for phase matching between plasmon mode and core guided mode. Alternate holes in the second layer coated with conducting metal oxide, i.e., indium tin oxide (ITO), contain analyte. We found that the optimized thickness of the ITO for optimum performance is 70 nm, which matches with reported result. Unlike other metal coated structures, here the resonance is around telecommunication window and can be tuned by varying the intrinsic properties of the ITO as per requirement. The proposed sensor shows refractive index sensitivity as high as 2000 nm/RIU and has resolution of 5×10-5 RIU.
167 citations
TL;DR: In this article, the photonic crystal fiber based surface plasmon resonance (PCF-SPR) chemical sensors were intensively reviewed, and the principles, superiorities and problems of the PCF-SRS sensors were also discussed in detail.
Abstract: Research developments of the photonic crystal fiber based surface plasmon resonance (PCF-SPR) chemical sensors were intensively reviewed Photonic crystal fibers, such as the microstructured optical fiber, the photonic bandgap fiber and the Bragg fiber with various structures were applied to the SPR sensors, including fuse-tapered fiber structure, D-type fiber structure and cladding-off fiber structure Those sensors were classified as three kinds of configurations which were respectively based on the inner metal layer, the metallic nanowire and the outer metal film What's more, the principles, superiorities and problems of the PCF-SPR sensors were also discussed in detail
164 citations
TL;DR: A novel type of few-mode fiber, characterized by an inverse-parabolic graded-index profile, is proposed for the robust transmission of cylindrical vector modes as well as modes carrying quantized orbital angular momentum (OAM).
Abstract: A novel type of few-mode fiber, characterized by an inverse-parabolic graded-index profile, is proposed for the robust transmission of cylindrical vector modes as well as modes carrying quantized orbital angular momentum (OAM). Large effective index separations between vector modes (>2.1 × 10−4) are numerically calculated and experimentally confirmed in this fiber over the whole C-band, enabling transmission of OAM(+/−1,1) modes for distances up to 1.1 km. Simple design rules are provided for the optimization of the fiber parameters.
164 citations
TL;DR: It is shown that realizable fiber structures can provide greatly improved performance in terms of leakage and bending losses compared to previously reported antiresonant fibers.
Abstract: An improved design for hollow antiresonant fibers (HAFs) is presented. It consists of adding extra antiresonant glass elements within the air cladding region of an antiresonant hollow-core fiber. We use numerical simulations to compare fiber structures with and without the additional cladding elements in the near- and mid-IR regimes. We show that realizable fiber structures can provide greatly improved performance in terms of leakage and bending losses compared to previously reported antiresonant fibers. At mid-IR wavelengths, the adoption of this novel fiber design will lead to HAFs with reduced bending losses. In the near-IR, this design could lead to the fabrication of HAFs with very low attenuation.
TL;DR: The ring laser resonator based on Er-doped active fiber with managed intracavity dispersion was capable of generating ultrashort optical pulses with full width at half maximum (FWHM) of 30 nm centered at 1565 nm.
Abstract: In this work we present for the first time, to the best of our knowledge, a stretched-pulse mode-locked fiber laser based on topological insulator. As a saturable absorber (SA) a ~0.5 mm thick lump of antimony telluride (Sb2Te3) deposited on a side-polished fiber was used. Such a SA introduced 6% modulation depth with 43% of non-saturable losses, which is sufficient for supporting stretched-pulse mode-locking. The ring laser resonator based on Er-doped active fiber with managed intracavity dispersion was capable of generating ultrashort optical pulses with full width at half maximum (FWHM) of 30 nm centered at 1565 nm. The pulses with duration of 128 fs were repeated with a frequency of 22.32 MHz.
TL;DR: The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V.
Abstract: We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V.
TL;DR: The first erbium-doped zirconium-fluoride-based glass fiber laser operating well beyond 3 μm with significant power and efficiency is reported, and it exhibited the longest wavelength of operation obtained to date for a room temperature, nonsupercontinuum fiber laser.
Abstract: We report the first, to the best of our knowledge, erbium-doped zirconium-fluoride-based glass fiber laser operating well beyond 3 μm with significant power. This fiber laser achieved 260 mW in CW at room temperature. The use of two different wavelength pump sources allows us to take advantage of the long-lived excited states that would normally cause a bottleneck, and this enables maximum incident optical-to-optical efficiency of 16% with respect to the total incident pump power. Both output power and efficiency are an order of magnitude improvement over similar lasers demonstrated previously. The fiber laser operating at 3.604 μm also exhibited the longest wavelength of operation obtained to date for a room temperature, nonsupercontinuum fiber laser.
TL;DR: Dispersive Fourier transformation is used to measure single-shot spectra of Raman-induced noise-like pulses, demonstrating that for low cavity gain values Raman emission is sporadic and follows rogue-wave-like probability distributions, while a saturated regime with Gaussian statistics is obtained for high pump powers.
Abstract: We report on an experimental study of spectral fluctuations induced by intracavity Raman conversion in a passively partially mode-locked, all-normal dispersion fiber laser. Specifically, we use dispersive Fourier transformation to measure single-shot spectra of Raman-induced noise-like pulses, demonstrating that for low cavity gain values Raman emission is sporadic and follows rogue-wave-like probability distributions, while a saturated regime with Gaussian statistics is obtained for high pump powers. Our experiments further reveal intracavity rogue waves originating from cascaded Raman dynamics.
TL;DR: In this paper, a novel birefringent photonic crystal fiber (PCF) biosensor constructed on the surface plasmon resonance (SPR) model is presented.
Abstract: A numerical analysis of a novel birefringent photonic crystal fiber (PCF) biosensor constructed on the surface plasmon resonance (SPR) model is presented in this paper. This biosensor configuration utilizes circular air holes to introduce birefringence into the structure. This PCF biosensor model shows promise in the area of multiple detection using HE
x
11
and HE
y
11
modes to sense more than one analyte. A numerical study of the biosensor is performed in two interrogation modes: amplitude and wavelength. Sensor resolution values with spectral interrogation yielded 5 × 10
-5
RIU (refractive index units) for HE
x
11
modes and 6 × 10
-5
RIU for HE
y
11
modes, whereas 3 × 10
-5
RIU for HE
x
11
modes and 4 × 10
-5
RIU for HE
y
11
modes are demonstrated for the amplitude interrogation.
TL;DR: Simple all-fiber three-mode multiplexers were made by adiabatically merging three dissimilar single-mode cores into one multimode core by collapsing air holes in a photonic crystal fiber and by fusing and tapering separate telecom fibers in a fluorine-doped silica capillary.
Abstract: Simple all-fiber three-mode multiplexers were made by adiabatically merging three dissimilar single-mode cores into one multimode core. This was achieved by collapsing air holes in a photonic crystal fiber and (in a separate device) by fusing and tapering separate telecom fibers in a fluorine-doped silica capillary. In each case the LP01 mode and both LP11 modes were individually excited from three separate input cores, with losses below 0.3 and 0.7 dB respectively and mode purities exceeding 10 dB. Scaling to more modes is challenging, but would be assisted by using single-mode fibers with a smaller ratio of cladding to core diameter.
TL;DR: This work fabricates a hollow antiresonant fiber which presents a bending loss as low as 0.25 dB/turn at a wavelength of 3.35 μm and a bend radius of 2.5 cm and uses numerical simulations to show that bending losses of hollowant fibers are a strong function of their geometrical structure.
Abstract: We first use numerical simulations to show that bending losses of hollow antiresonant fibers are a strong function of their geometrical structure. We then demonstrate this by fabricating a hollow antiresonant fiber which presents a bending loss as low as 0.25dB/turn at a wavelength of 3.35μm and a bend radius of 2.5cm. This fiber has a relatively low attenuation (<200dB/km) over 600nm mid-infrared spectral range.
TL;DR: A highly sensitive fiber-optic sensor based on two cascaded intrinsic fiber Fabry-Perot interferometers (IFFPIs) is reported and it is found that the strain sensitivity of the proposed sensor can be improved from 1.6 pm/με for a single IFFPI sensor to 47.14 pm/ με by employing the Vernier effect.
Abstract: We report a highly sensitive fiber-optic sensor based on two cascaded intrinsic fiber Fabry-Perot interferometers (IFFPIs). The cascaded IFFPIs have different free spectral ranges (FSRs) and are formed by a short section of hollow core photonic crystal fiber sandwiched by two single mode fibers. With the superposition of reflective spectrum with different FSRs, the Vernier effect will be generated in the proposed sensor and we found that the strain sensitivity of the proposed sensor can be improved from 1.6 pm/μe for a single IFFPI sensor to 47.14 pm/μe by employing the Vernier effect. The sensor embed with a metglas ribbon can be also used to measure the magnetic field according to the similar principle. The sensitivity of the magnetic field measurement is achieved to be 71.57 pm/Oe that is significantly larger than the 2.5 pm/Oe for a single IFFPI sensor.
TL;DR: An acoustic- and gain-tailored Yb-doped polarization-maintaining photonic crystal fiber is used to demonstrate 811 W single-frequency output power with near diffraction-limited beam quality, which represents the highest power ever reported from a near diffractions-limited single- frequencies fiber laser.
Abstract: An acoustic- and gain-tailored Yb-doped polarization-maintaining photonic crystal fiber is used to demonstrate 811 W single-frequency output power with near diffraction-limited beam quality. The fiber core is composed of 7 individually doped segments arranged to create three distinct transverse acoustic regions; including one region that is Yb-free. The utility of the Yb-free region is to reduce coupling between the LP01 and LP11 modes to mitigate the modal instability. The application of thermal gradients is utilized in conjunction with the transverse acoustic tailoring to suppress stimulated Brillouin scattering. To the best of our knowledge, the 811 W output represents the highest power ever reported from a near diffraction-limited single-frequency fiber laser.
TL;DR: In this article, the authors reported broadband (up to ~1000 nm) ultrafast pulse generation from three fiber lasers mode-locked by a single graphene saturable absorber device, based on Yb-, Er- and Tm:Ho-doped fiber lasers at the central wavelength of 1035, 1564, and 1908 nm, respectively.
Abstract: Ultrafast fiber lasers with broad spectral coverage are in great demand for a variety of applications, such as spectroscopy, and biomedical diagnosis. Graphene is an ideal ultrawide-band saturable absorber. We report broadband (up to ~1000 nm) ultrafast pulse generation from three fiber lasers mode-locked by a single graphene saturable absorber device. The mode-locked pulses were based on Yb-, Er- and Tm:Ho-doped fiber lasers at the central wavelength of 1035, 1564, and 1908 nm, respectively. The maximum output energy is up to 16.2 nJ at 1908 nm. It is the first time that ultrafast fiber lasers covering 1, 1.5, and 2 μm spectral region are mode-locked with a single graphene device. Our results validate the intrinsic broadband operation property of graphene devices for all major fiber laser wavelengths from 1 to 2 μm.
TL;DR: In this article, a surface plasmon resonance (SPR) sensor based on a single mode optical fiber with six air holes is proposed, where a thin gold film and a TiO2 film are deposited on the walls of air holes.
TL;DR: A novel approach for generating Mid-InfraRed SuperContinuum (MIR SC) by using concatenated fluoride and chalcogenide glass fibers pumped with a standard pulsed Thulium laser is theoretically demonstrated.
Abstract: We theoretically demonstrate a novel approach for generating Mid-InfraRed SuperContinuum (MIR SC) by using concatenated fluoride and chalcogenide glass fibers pumped with a standard pulsed Thulium (Tm) laser (TFWHM=3.5ps, P0=20kW, νR=30MHz, and Pavg=2W). The fluoride fiber SC is generated in 10m of ZBLAN spanning the 0.9–4.1μm SC at the −30dB level. The ZBLAN fiber SC is then coupled into 10cm of As2Se3 chalcogenide Microstructured Optical Fiber (MOF) designed to have a zero-dispersion wavelength (λZDW) significantly below the 4.1μm InfraRed (IR) edge of the ZBLAN fiber SC, here 3.55μm. This allows the MIR solitons in the ZBLAN fiber SC to couple into anomalous dispersion in the chalcogenide fiber and further redshift out to the fiber loss edge at around 9μm. The final 0.9–9μm SC covers over 3 octaves in the MIR with around 15mW of power converted into the 6–9μm range.
TL;DR: To the best of the knowledge, this is the first report of an octave-spanning, all-normal dispersion supercontinuum generation in a non-silica microstructured fiber, where the spectrum long-wavelength edge is red-shifted to as far as 2300 nm.
Abstract: Supercontinuum spanning over an octave from 900 – 2300 nm is reported in an all-normal dispersion, soft glass photonic crystal fiber. The all-solid microstructured fiber was engineered to achieve a normal dispersion profile flattened to within −50 to −30 ps/nm/km in the wavelength range of 1100 – 2700 nm. Under pumping with 75 fs pulses centered at 1550 nm, the recorded spectral flatness is 7 dB in the 930 – 2170 nm range, and significantly less if cladding modes present in the uncoated photonic crystal fiber are removed. To the best of our knowledge, this is the first report of an octave-spanning, all-normal dispersion supercontinuum generation in a non-silica microstructured fiber, where the spectrum long-wavelength edge is red-shifted to as far as 2300 nm. This is also an important step in moving the concept of ultrafast coherent supercontinuum generation in all-normal dispersion fibers further towards the mid-infrared spectral region.
TL;DR: In this paper, a number of propagation characteristics of hexagonal and octagonal photonic crystal fiber structures, where both core and cladding are microstructured, have been investigated by employing the full vectorial finite element method (FEM).
20 Sep 2014
TL;DR: In this article, the authors studied the properties of a helically twisted photonic crystal fiber (PCF) that preserves the chirality of OAM modes of the same order, i.e., it inhibits scattering between an order + 1 mode to an order − 1 mode.
Abstract: In optical fiber telecommunications, there is much current work on the use of orbital angular momentum (OAM) modes for increasing channel capacity. Here we study the properties of a helically twisted photonic crystal fiber (PCF) that preserves the chirality of OAM modes of the same order, i.e., it inhibits scattering between an order +1 mode to an order −1 mode. This is achieved by thermally inducing a helical twist in a PCF with a novel three-bladed Y-shaped core. The effect is seen for twist periods of a few millimeters or less. We develop a novel scalar theory to analyze the properties of the twisted fiber, based on a helicoidal extension to Bloch wave theory. It yields results that are in excellent agreement with full finite element simulations. Since twisted PCFs with complex core structures can be produced in long lengths from a fiber drawing tower, they are of potential interest for increasing channel capacity in optical telecommunications, but the result is also of interest to the photonic crystal community, where a new kind of guided helical Bloch mode is sure to excite interest, and among the spin–orbit coupling community.
TL;DR: A novel fiber in-line Mach-Zehnder interferometer with a large fringe visibility of up to 17 dB, which was fabricated by misaligned splicing a short section of thin core fiber between two sections of standard single-mode fiber could be used to realize simultaneous measurement of tensile strain and temperature.
Abstract: We demonstrated a novel fiber in-line Mach-Zehnder interferometer (MZI) with a large fringe visibility of up to 17 dB, which was fabricated by misaligned splicing a short section of thin core fiber between two sections of standard single-mode fiber. Such a MZI could be used to realize simultaneous measurement of tensile strain and temperature. Tensile strain was measured with an ultrahigh sensitivity of −0.023 dB/μɛ via the intensity modulation of interference fringes, and temperature was measured with a high sensitivity of 51 pm/°C via the wavelength modulation of interference fringe. That is, the MZI-based sensor overcomes the cross-sensitivity problem between tensile strain and temperature by means of different demodulation methods. Moreover, this proposed sensor exhibits the advantages of low-cost, extremely simple structure, compact size (only about 10 mm), and good repeatability.
TL;DR: Damage-free fiber-guidance of milli-Joule energy-level and 600-femtosecond laser pulses into hypocycloid core-contour Kagome hollow-core photonic crystal fibers and free focusing-optics laser-micromachining was demonstrated on different materials.
Abstract: We report on damage-free fiber-guidance of milli-Joule energy-level and 600-femtosecond laser pulses into hypocycloid core-contour Kagome hollow-core photonic crystal fibers. Up to 10 meter-long fibers were used to successfully deliver Yb-laser pulses in robustly single-mode fashion. Different pulse propagation regimes were demonstrated by simply changing the fiber dispersion and gas. Self-compression to ~50 fs, and intensity-level nearing petawatt/cm(2) were achieved. Finally, free focusing-optics laser-micromachining was also demonstrated on different materials.
TL;DR: A broad review of microstructured fiber optics components, including light guides, image guides, multicapillary arrays, and photonic crystal fibers, is given in this article, where the authors discuss fundamental aspects of stack-and-draw technology used at ITME, through design methods, soft glass material issues and parameters.
Abstract: A broad review is given of microstructured fiber optics components – light guides, image guides, multicapillary arrays, and photonic crystal fibers – fabricated using the stack-and-draw method from various in-house synthesized oxide soft glasses at the Glass Department of the Institute of Electronic Materials Technology (ITME). The discussion covers fundamental aspects of stack-and-draw technology used at ITME, through design methods, soft glass material issues and parameters, to demonstration of representative examples of fabricated structures and an experimental characterization of their optical properties and results obtained in typical applications. Specifically, demonstrators include microstructured image guides providing resolution of up to 16000 pixels sized up to 20 μm in diameter, and various photonic crystal fibers (PCFs): index-guiding regular lattice air-hole PCFs, hollow core photonic bandgap PCFs, or specialty PCFs like highly birefringent microstructured fibers or highly nonlinear fibers for supercontinuum generation. The presented content is put into context of previous work in the area reported by the group of authors, as well as other research teams.
TL;DR: In this paper, a curvature sensor based on optical fiber modal interferometer is proposed, which consists of two peanut-shape structures that are formed only by single mode fibers.
Abstract: A novel curvature sensor based on optical fiber modal interferometer is demonstrated. It consists of two peanut-shape structures that are formed only by single mode fibers. The two peanut-shape structures can split and recombine the core and cladding modes, consequently, it produces modal interference. The experimental results show that the shift of the peak wavelength is almost linearly proportional to the change of curvature, and the sensitivities of the sensors with the lengths of 21, 26, and 30 mm are -18.46, -21.87, and 13.68 nm/m-1, respectively. The proposed curvature sensor is simple, high sensitive, and inexpensive.