Low-loss Splicing Research Articles

Compact and Low-Loss ZrO2-SiO2PLC-Based 8 × 8 Multicast Switch for CDC-ROADM Application

In this paper, we report design and characteristics of a compact and low-loss multicast switch (MCS) based on a high Δ planar lightwave circuit (PLC) which consists of ZrO2 doped silica glass. Chip size of an 8 × 8 MCS consists of an eight-arrayed 1 × 8 splitter and an eight-arrayed 8 × 1 switch is reduced to 30 mm × 9 mm by using the ZrO2-SiO2 PLC with 5.5%-Δ. Eight-input and eight-output ports of the MCS are arrayed at the one side of the chip, and coupled to optical fibers with a 16-fiber V-groove array. A high Δ fiber is used to reduce coupling loss to the ZrO2-SiO2 PLC, and the high Δ fiber is spliced to a single-mode fiber (SMF) by using low-loss splicing technique. Coupling loss between the ZrO2-SiO2 PLC and the SMF is reduced to 0.4 dB/facet. Average insertion loss of the fabricated MCS is 12.8 dB including coupling loss to the SMF. Extinction ratio and polarization dependent loss of the MCS are over 50 dB and less than 0.5 dB in L-band, respectively.

An Effective Thermal Splicing Method to Join Fluoride and Silica Fibers for a High Power Regime**Supported by the National Natural Science Foundation of China under Grant No 61275144, the Innovative Research and Development Project of Nanshan District under Grant No KC2013JSCX0013A, the Shenzhen Science and Technology Innovation Projects under Grant No JCYJ20150324140036862, and the Funding from Shenzhen University under Grant

A repeatable and simple thermal splicing method for low loss splice between fluoride and silica fibers is presented. The minimum splicing loss of 0.58 dB is achieved experimentally with this approach. Meanwhile, the power capacity of this splicing joint is also tested with a high power fiber laser. The maximum input power is up to 15 W, only limited by the available power of the laser source. To the best of our knowledge, this is the first report on thermal splicing between fluoride and silica fibers operating in a high power regime without any complicated ion-assisted deposition process.

2 kW CW near single mode all-fiber Ytterbium-doped fiber laser

We demonstrated a CW all-fiber Ytterbium-doped fiber laser with master oscillator power amplifier configuration. The laser system generated 2.04kW output power at 1080nm with 78.5% total optical-to-optical efficiency. What is more, the output laser was near single mode with the beam quality factor M2<1.37 at the maximum power. It benefited from low splicing loss, proper heat management and effective controlling of fiber facet damage and the nonlinear effects through optimizing the whole system. The analysis showed that higher output power could be achieved with more pump power in this laser system.

Splice Loss Optimization of a Photonic Bandgap Fiber via a High V-Number Fiber

We report on a low-loss fusion splice between a hollow-core photonic bandgap fiber (NKT's HC-1550-02) and a conventional single mode fiber (Corning's SMF28) using a high V-number intermediate fiber. Compared to the commonly used fiber postprocessing techniques, the intermediate fiber method offers a new adjusting degree of freedom of V-numbers, enabling the reduction of coupling loss to 0.35 dB. Experimentally, a low fusion splice loss of 0.63 dB has been achieved between Nufern's SM1950 (V =2.836) and HC-1550-02 fiber, resulting in an overall insertion loss of 0.73 dB from SMF28 to HC-1550-02 fiber. We believe this is the lowest splice loss value reported for HC-1550-02 fiber using an arc splicer, on the aspect of both using a step-index solid-core fiber (0.63 dB) and a SMF28 fiber (0.73 dB).

Gaussian-Like Mode Field Generated in a Seven-Core Photonic Crystal Fiber for Low Loss Splicing by Air Hole Collapse Technique

Multicore photonic crystal fiber is an important research direction to realize high-power supercontiuum. We report two post processing methods based on air hole collapse technique to generate Gaussian-like mode field in a seven-core photonic crystal fiber (SCPCF) for low loss splicing. By heating and collapsing all air holes in the meantime, the mode field of SCPCF becomes more concentrated and the valleys between separated core modes become much flatter. Another method to generate Gaussian-like mode field is selectively collapsing the central air holes between the seven cores, which can form an integrated larger core. Theoretical simulation results are confirmed by experiment and both methods are used to decrease mode field mismatch between SCPCF and double clad fiber with splicing losses as low as 0.46 and 0.22 dB, respectively.

Low Loss Splicing Between Double-Clad Fiber and Photonic Crystal Fiber Using Graded Index Fiber Lens

A novel approach of splicing between photonic crystal fiber (PCF) and double-clad fiber is demonstrated with the utilization of graded index fiber (GIF) and coreless fiber as fiber lens. The light beam in large core double-clad fiber is first enlarged by coreless fiber and then focused by GIF to match the small core PCF to realize the low loss splicing. The splicing losses versus the length of GIF, coreless fiber as well as the air hole collapsed region were investigated theoretically and experimentally. Through tailoring the length of GIF and coreless fiber precisely, a splicing loss as low as 0.5 dB was finally achieved between double-clad fiber and PCF with the mode field diameters of 18.7 and 3.9 μm, respectively. To the best of our knowledge, this is the first time to achieve such a low splicing loss between double-clad fiber and PCF.

Ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber

An ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber is proposed. Two fluorine-doped cores and a central microstructured modulation core are introduced to achieve an excellent performance and an ultrawide bandwidth. Numerical simulation demonstrates that the splitter has a bandwidth as wide as 300nm, with an extinction ratio (ER) as low as -20 dB. At the wavelength of 1.55μm, the ER reaches -30 dB. All the air holes in our design are circular holes and are arranged in a triangular lattice that is easy to fabricate with the method of stack and draw. A suitable mode field area and a Gaussian-like mode field distribution lead to a low splicing loss that is as low as 0.04dB when splicing with standard single-mode fibers as the lead-in and lead-out ports.

Splicing of index-guiding microstructured optical fibers and single-mode fibers by controlled air-hole collapse: an analytical approach

Low-loss splicing of index-guiding microstructured optical fibers (MOFs) and conventional single-mode fibers (SMFs) can be achieved by enlarging the mode field diameter of MOFs, which leads to an optimum mode field match at the joint interface. We study analytically the low-loss fusion splicing between an MOF and an SMF by expanding the modal field of MOF, using the controlled air-hole collapse method. Our method is simple and offers analytical solution for light coupling between MOFs and SMFs. Comparisons with available experimental and simulation results have also been included.

Pressure-assisted low-loss fusion splicing between photonic crystal fiber and single-mode fiber.

We demonstrate low-loss splicing between a photonic crystal fiber (PCF) and a single-mode fiber (SMF) with a conventional electric-arc fusion splicer, where nitrogen gas (N2) with a proper pressure is pumped into the air holes of the PCF to control the air-hole collapse ratio so as to optimize the mode-field match at the joint. The method is applicable to both solid-core and hollow-core PCFs. With this method, we achieve a splice loss (measured at 1550 nm) of ~0.40 dB for a solid-core PCF and ~1.05 dB for a hollow-core PCF. The method could find wide applications in the fabrication of PCF-based devices.

Dispersion control in square lattice photonic crystal fiber using hollow ring defects

We propose a new dispersion control scheme by introducing hollow ring defects having a central air hole and a GeO2-or F-doped silica ring with in a square lattice photonic crystal fiber. We confirmed the flexible dispersion controllability in the proposed structure in two aspects of dispersion managements: ultra-flattened near-zero dispersion in the 530 nm-bandwidth over all communication bands and dispersion compensation in C, L, and U band with a high compensation ratio of 0.96~1.0 in reference to the standard single mode fiber. The proposed SLPCFs were also estimated to have an inherently low splice loss due to the index contrast between the doped-ring and silica that kept a good guidance even along with collapsed air holes, which cannot be achieved in conventional PCFs.

Design and optimization of a novel broadband and polarization-insensitive dual-core photonic crystal fiber coupler over the whole optical communication band

In this paper, a novel broadband polarization-insensitive dual-core photonic crystal fiber with elliptical central hole is proposed and the influence of its structural parameters on coupling characteristic is investigated in detail by the full-vector finite element method. Through optimizing the fiber structural parameters, broadband and polarization-insensitive characteristics are achieved over the whole optical communication band from 1.225 m to 1.675 m. The variation of coupling ratio is stabilized at 50% 1%, and the coupling ratio difference between x polarization and y polarization is less than 0.5% overall the wavelength range. Due to its relatively independent of cores and elliptical central hole and suitable structural parameters, this fiber meets the application requirements, that is, easy to fabricate, easy to splice and low splice loss. This research is freed from the current coupler limit: narrow bandwidth, wavelength dependence, polarization-sensitive, difficulty of fabricating, thereby provides the theoretical basis for the study of the large capacity high speed all-optical networks and multi-wavelength tunable fiber laser.

All-fiber 177.6 W supercontinuum source

Supercontinuum has wide and important applications in a range of fields, so it is one of the hot research spots in recent years. In this paper the mechanism and the latest achievements in high power supercontinuum generation under continuous wave laser pump and pulsed laser pump regimes during the past several years are reviewed. The challenges and the problems that need to overcome in scaling the average output power of supercontinuum generation are analyzed. An all-fiber supercontinuum source constructed at the national university of defense technology is demonstrated with 177.6 W average output power which overcomes the problems of low splicing loss, facet damage of the output fiber, the heat treatment and the effective control of the nonlinear effects through the optimization of the whole system. To the best of the author's knowledge, the 177.6 W average output power is the highest value in ever reported ones.

基于光纤拉锥模场匹配技术的光子晶体光纤低损耗熔接

基于光纤拉锥模场匹配技术的光子晶体光纤低损耗熔接

Low-Loss Fusion Splicing Photonic Crystal Fibers and Double Cladding Fibers by Controlled Hole Collapse and Tapering

We demonstrate a novel method for low-loss splicing photonic crystal fibers (PCFs) and double cladding fibers (DCFs) by controlled hole collapse and tapering using a conventional fusion splicer. Through controlled hole collapse, two center rings of holes were collapsed to expand the core of the PCF, while the cladding diameter of the PCF was almostly not changed. The mode field diameter (MFD) and inner cladding diameter of the DCFs were decreased by tapering. So an optimum mode field and cladding match at the interface of PCF-DCF and an adiabatic mode field variation in the longitudinal direction of the PCF and DCF can be achieved. This is the first time, to our knowledge, to realize low-loss splicing between the DCFs and PCFs. Splice losses as low as 0.65 dB were achieved between a PCF and a DCF with MFDs of 5.8 and 26.5 μm, and with the inner cladding diameters of 125 and 250 μm, respectively.

Low-Loss Patch Cords by Effective Splicing of Various Photonic Crystal Fibers With Standard Single Mode Fiber

We report on low-loss patch cords composed of a highly reproducible low-loss fusion splicing of photonic crystal fibers (PCFs) with a standard single mode fiber (SMF). Distinct from other papers in this area we report on the results for different types of PCFs, including LMA fibers with similar to a SMF core size and a mode field diameter (MFD), as well as polarization maintaining (PM) Bow-Tie PCF with an elliptical GeO 2 doped core and also a suspended-core (SC) PCF with a tiny core. We show that all studied splices between SMF and PCFs exhibit dispersive and non-reciprocal, in view of a light propagation direction, transmission losses. Defined as a larger decrease of a transmitted optical power comparing both propagation directions, achieved splicing losses, are equal to 0.46 ±0.03 dB, 0.34±0.01 dB, 0.67 ±0.17 dB and 3.09 ±0.36 dB at 1550 nm for LMA8, LMA10, Bow-Tie PCF and SC PCFs, respectively. Moreover, additionally to developed low-loss splicing, we report on low-loss patch cords for all mentioned above PCFs spliced on both ends with SMF pigtails ended with FC/APC connectors achieving the total losses at 1550 nm equal to 1.07 ±0.07 dB for LMA8, 0.72 ±0.20 dB for LMA10, 1.30 ±0.06 dB for Bow-Tie PCF, and 9.36 ±0.20 dB for SC PCF.

Designing high performance Er +3-doped fiber amplifier in triangular-lattice photonic crystal fiber host towards higher gain, low splice loss

In order to improve the over-all performance of all-fiber amplifier using Er +3-doped triangular-lattice photonic crystal fiber (PCF), we performed a detailed study on the amplifying characteristics of the PCF host by varying all associated geometrical parameters towards utilizing controllable effective numerical aperture and tight modal confinement. A finite difference (FD) mode convergence analysis is used to determine the modal propagation characteristics of the structure, which is then used to solve a standard propagation and population rate equation. Our results show that a spectral gain of the amplifier as high as 51 dB and that too over a short length ∼2.5 m of the fiber is achievable by optimizing the transverse geometry of the fiber. Aimed at field-deployment of the amplifier as inline component, we calculate the important all-fiber characteristics, namely, beam divergence, bending loss and nonlinearity and then optimize the splicing/coupling loss (resulting from the fundamental mode mismatch only) of this active fiber device. Notably, the splice loss with standard telecom-grade SMF-28 fiber is considerably minimized through an improved mode-matching of the design. These results record a marked improvement in fiber amplifier research in realizing high-performance EDFA-PCF amplifiers.

20 W all fiber supercontinuum generation from picosecond MOPA pumped photonic crystal fiber

An all fiber high power supercontinuum (SC) source is demonstrated by pumping a section of photonic crystal fiber (PCF) with a picosecond MOPA laser. The core of the PCF is enlarged at the input end through a serious of PCF post processing method to match the output fiber of the picosecond laser, to ensure low loss splicing, hence high power operation of the whole system. The supercontinuum output spectrum covers the wavelength range from 650 nm to beyond 1700 nm. Limited by available pump power, 20 W super-continuum output power is obtained under 29.5 W picosecond pump power, giving a high optical to optical conversion efficiency of 67.8%.

Twin-core fiber fabrication for exciting and detecting signals easily

A twin-core fiber (TCF) with noncircular cross section has been fabricated.The two cores of the TCF can be easily identified. It has been demonstrated that signals can be easily excited and detected in this TCF, by splicing a single-mode fiber to either of the TCF cores. The splice loss below 1 dB has been repeatedly obtained. Mutual splicing of these TCFs with low splice loss, by using a commercial fusion splicer, has also been demonstrated. The splice loss below 1.5 dB has been repeatedly obtained. Optical devices based on this TCF may be easily inserted into a standard SMF. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:499–502, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25792

Design of dual-mode optical fibres for the FTTH applications

We present in this article a proposal and design for dual-mode optical fibres forfibre-to-the-home applications. High-order modes in the fibre can be effectively suppressedby the connection of the fibre with standard single-mode optical fibres at the two ends ofthe fibre. The alignment tolerance at the splicing process is presented. In particular, a lowbending loss operation with low splice loss is demonstrated using the proposed technique.

Ultra-short distributed feedback fiber laser with sub-kilohertz linewidth for sensing applications

A low-noise, ultra-short linear-cavity distributed feedback fiber laser (DFB-FL) with extremely narrow linewidth is presented. The FL has a total length of 17 mm, which is, to our knowledge, the shortest DFB-FL being reported. It has a measured linewidth of merely 250 Hz without active stabilization. It has a polarization beat frequency of 101 MHz, which is several times lower than that of most FLs. The relaxation oscillation frequency and relative peak are 110 kHz and −76.5 dB/Hz, respectively. The FL exhibited low-noise characteristics, with an intensity noise of −107 dB/Hz at 1 MHz. Due to low dopant concentration of the EDF and low splice loss with ordinary single-mode fibers, the net insertion loss amounts to only 0.45 dB. Such low pump power loss greatly enhances the capability of multiplexing a large number of FL sensors. Thus, these ultra-short DFB-FLs open up new opportunities for the development of compact-sized point sensor array systems for large-scale high sensitivity sensing applications.