Fiber Splicing Research Articles

Silica/Electro-Optic Polymer Optical Modulator With Integrated Antenna for Microwave Receiving

A silica/electro-optic (EO) polymer phase modulator is proposed for microwave radiation receiver with the use of a bowtie antenna. Waveguide design optimization is presented for a waveguide with an EO polymer core and silica/sol-gel cladding. Electrode effects on the insertion loss and poling efficiency are also analyzed and conditions for low-loss and high poling efficiency established. The bowtie antenna is simulated and shows a broadband response with a maximum at 5 GHz and a 3 dB-bandwidth of approximately 12 GHz. A fiber splicing technique is presented that reduces coupling loss between SMF-28 and the waveguide. Experimental results for a fabricated device with microwave-response between 10-14 GHz are shown with carrier to first sideband intensity difference of up to -36 dB.

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.

Nondestructive Three-Dimensional Observation of the Influence of Zirconium Inclusions in Laser-Irradiated Fusion-Spliced Optical Fiber on Core Structure Changes Using Synchrotron Radiation X-ray Micro-Computed Tomography

In this paper, we describe a nondestructive method of observing changes in the microstructure of optical fibers subjected to CO2 laser irradiation for optical fiber splicing using synchrotron radiation micro-computed tomography (CT). In particular, we evaluated a method of enhancing the contrast between a GeO2-doped optical fiber core and a silica cladding by performing CT observations of the X-ray energy around the Ge-K absorption edge. Specifically, procedures for extracting a GeO2-doped core from a three-dimensional image of optical fibers by the cluster labeling method are proposed and evaluated. The approach enabled us to observe how inclusions at the optical fiber splicing interface influence the optical fiber core structure. We also expect this observation method to be used for improving such aspects of laser processing performance as insertion loss and mechanical strength for recently developed optical fibers.

Novel field installable optical fiber splice and connector for optical access networks

We have developed two types of field installable connection techniques. One is mechanical splicing, which is used to connect coated optical fibers without the need for stripping or cleaning procedures. The other is a field assembly connection technique, which employs a new type of field installable connector that makes it possible to realize a physical contact connection with chamfer grinding. Mechanical splicing is achieved by precisely aligning and directly connecting coated fibers with a capillary. The assembled splice is installed with 1.3-μm single-mode fibers that have an 80-μm cladding and a 125-μm coating and they exhibit good optical performance with a low average insertion loss of 0.2dB. Connection is achieved with our developed field installable connector by using a chamfered fiber endface and the compression force of the buckled fiber. The assembled connectors achieve physical contact with the chamfered fiber endface, which provides good optical performance with a low insertion loss of 0.11dB.

The influence of fusion splicing on the beam quality of a ytterbium-doped fiber laser

Ytterbium-doped fiber lasers are attractive in many fields due to their high output power and good beam quality. Meanwhile, fiber fusion splicing—a necessary and inevitable process in building a fiber laser—could affect not only the output power but also the output beam quality of a fiber laser. The influences of fusion splicing on laser beam quality are studied and discussed in this paper. A model based on the beam propagation method and computation of the M2 factor is employed to research the effects of fiber splicing. Different cases of spatial deviation during fusion splicing, including shifting and tilting, are simulated. Fiber splicing with drift in one and two dimensions is investigated as well, the results of which show good agreement with the simulated ones. Furthermore, the effects of splice shifting and tilting on laser beam quality are compared to select the most critical one. Beam quality variations under different circumstances, such as deviation direction, fiber type, and input beam quality, are also discussed.

Splice loss requirements in multi-mode fiber mode-division-multiplex transmission links

We investigate numerically the influence of fiber splices and fiber connectors to the statistics of mode dependent loss (MDL) and multiple-input multiple-output (MIMO) outage capacity in mode multiplexed multi-mode fiber links. Our results indicate required splice losses much lower than currently feasible to achieve a reasonable outage capacity in long-haul transmission systems. Splice losses as low as 0.03dB may effectively lead to an outage of MIMO channels after only a few hundred kilometers transmission length. In a first approximation, the relative capacity solely depends on the accumulated splice loss and should be less than ≈ 2dB to ensure a relative capacity of 90%. We also show that discrete mode permutation (mixing) within the transmission line may effectively increase the maximum transmission distance by a factor of 5 for conventional splice losses.

A Raman amplified GPON reach extension system using parameters of a deployed fiber

Recently distributed Raman amplification of the upstream signal has been proposed to improve the loss budget for gigabit passive optical networks (GPON), and systems of 60-km reach and up to 128 way split have been demonstrated employing state-of-the-art fibers. However, a deployed fiber plant may not perform as well due to elevated fiber attenuation, splice losses, and back-reflections that are present in a realistic GPON system. In this paper, their effects on the Raman amplified 1310-nm upstream signal in a GPON reach extension system is investigated numerically. Using the parameters of a deployed fiber, a design solution is provided for a purely passive, Raman amplified GPON reach extender. Results show that 55-km logical reach and 1:32 split ratio can be achieved using a realistic fiber plant and class B + transceivers.

Simple In-Line M–Z Interferometer Based on Dual-Core Photonic Crystal Fiber

We experimentally demonstrated a simple dual-core photonic-crystal-fiber-based M-Z interferometer by use of femtosecond laser drilling and fiber splicing. A higher order mode is excited in one fiber core by introducing a conical air hole at the splice point, which interferes with the fundamental mode in the other fiber core. Sensing applications to strain and temperature of the interferometer are experimentally demonstrated in this letter, and the sensitivities are obtained to be 2.18 pm/μe and 6.8 pm/ °C, respectively. The device is compact and robust with a very simple structure, and can find applications in liquid environment.

Manufacturing Task Process Characterization Utilizing Response Surface Methodology

To meet today’s business culture of rapid deployment of new products and processes, engineering and manufacturing personnel must utilize efficient means for process development. This paper discusses a novel approach to characterize a task driven manufacturing process. The approach utilized Response Surface Methodology (RSM) to investigate, identify, and prioritize the key process drivers and subsequently develop quantifiable methods for setting the operating levels for the process drivers to determine if the current levels of these key process drivers result in a process response value that is near optimum. The approach identifies the improved response region, generates a mathematical model of the process and specifies an operating window that would yield consistent results for each of the process drivers. A High Strength Fiber Splicing process was used to demonstrate this approach. This study led to the identification of the region that improved the process yield from 65% to 85%.

All-solid photonic band gap fiber based distributed fiber optic pressure sensor

A novel distributed fiber optic pressure sensor based on an all-solid photonic band gap fiber is proposed and experimentally demonstrated. The sensor is fabricated by splicing a piece of the photonic crystal fiber (PCF) with a single-mode fiber (SMF), and the free end face of the PCF is filmed with a reflectivity of 99%. The cladding mode is excited at the fiber splice, resulting in the interference between the cladding mode and the core mode. The pressure position can be located by measuring the phase difference of the interferometer, and the pressure can be interrogated by measuring the height of the valley in the white-light optical spectrum. The experimental results show that the pressure and its position along the PCF can be simultaneously interrogated.

A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper

A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity.

Mechanical Splice Characteristics of a Hole-Assisted Fiber

The mechanical splice characteristics of a single-mode hole-assisted fiber (SM-HAF) are investigated both numerically and experimentally. Mode-coupling theory is used to investigate the mechanical splice loss characteristic of the HAF. We introduced an air filling fraction and a \bm V-parameter to allow us to consider an HAF with arbitrary structural parameters. We derive the optimum conditions (e.g., refractive index and temperature coefficient) of a solid-type refractive index matching material to realize good splice and return loss characteristics simultaneously. The validity of the derived conditions is investigated experimentally. Finally, we confirm that we can achieve comparable splice characteristics to those of conventional single-mode fiber splices by using the optimized refractive index matching material independent of the structural parameters of the SM-HAF.

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.

Distributed Model for Actively Q-Switched Erbium-Doped Fiber Lasers

A distributed laser model is applied to explain the multi-peak shape of the pulses generated by the actively Q-switched erbium-doped fiber laser. In the model, all kinds of intra-cavity losses are taken into account, including the point losses produced by fiber splices and intra-cavity elements, and the distributed loss, such as the active fiber background loss and the loss caused by excited state absorption inherent in erbium-doped fibers. The model also takes into account the exact function that describes the switching dynamics of the Q-switch modulator. We show that the distributed model allows an accurate simulation of the laser pulse shape and energy, providing therefore a good agreement with the experimental results. The origin of a multi-peak pulse shape frequently observed in QS-EDFL and some other features that result from the model are discussed.

Multipass Hollow Core-PCF Microcell Using a Tapered Micromirror

We demonstrate the insertion of a micromirror into the core of a hollow core photonic crystal fiber (HC-PCF). The micromirror is formed from a single mode fiber that has been tapered to fit into the hollow core and fixed in place using a fusion splicer. A large range of reflectivities higher than 4% was also achieved by silver-coating the silica tapered-fiber end-face using thermal evaporation. The current micromirror provides two key advantages over using a full-sized fiber splice to create a reflective interface. First, the tapered fiber tip can be coated to increase the reflectivity without degradation due to heating during the splicing process. Second, increased efficiency of input and output coupling is possible because of improved mode-field overlap with the fundamental mode of the HC-PCF. We show potential applications of micromirrors for the formation of microcavities in hollow-core fibers and for gas saturated absorption spectroscopy.

SPring-8 X-Ray Micro-Tomography Observations of Zirconium Inclusions in CO$_{2}$ Laser Fusion Splice for Single Mode Optical Fibers

Laser fusion splicing has been realized for the simple splicing of optical fibers in a small board area, and for accommodating the increasing number of optical fibers that must be mounted on a board. For the splicing, zirconia ceramics are conventionally used to fabricate V-groove substrates because of their high machining performance. In this study, the existence of zirconium inclusions between the spliced optical fibers could be clarified with SPring-8 micro-computed tomography (SP-μCT) for the first time. The large inclusion size was found to increase the splicing loss. Moreover, the average splicing loss could be reduced from 0.18 dB to 0.15 dB by the adoption of a cleaning process to remove the zirconium inclusions that originate from the V-groove substrate used for the fiber.

Fusion Splicing of Elliptical Core Optical Fibers

Fusion splicing of elliptical core optical fibers is investigated in detail. A formula is derived for how the ellipticity of the mode fields contributes to splice loss. It is shown experimentally that even fibers with rather high mode field ellipticity can be fusion spliced with relatively low loss due to dopant diffusion. It is further shown that the polarization extinction ratio can be maintained at an adequate level.

Design and performance of ultra-high-density optical fiber cable with rollable optical fiber ribbons

This paper proposes a novel ultra-high-density optical fiber cable that employs rollable optical fiber ribbons. The cable has great advantages in terms of cable weight and diameter, and fiber splicing workability. Moreover, it will be easy to install in a small space in underground ducts and on residential and business premises. The structural design of the rollable optical fiber ribbon is evaluated theoretically and experimentally, and an optimum adhesion pitch P in the longitudinal direction is obtained. In addition, we examined the performance of ultra-high-density cables with a small diameter that employ rollable optical fiber ribbons and bending-loss insensitive optical fibers. The transmission, mechanical and mid-span access performance of these cables was confirmed to be excellent.

Novel Optical Fiber Cable with Small Cable Diameter Employing Rollable 20-Fiber Ribbons

This letter proposes novel optical fiber cables with extremely small cable diameter that employs rollable 20-fiber ribbons, which will improve fiber ribbon and cable productivity compared with optical fiber cable employing rollable 4-fiber ribbons. We fabricated the cables and investigated its feasibility in terms of high-count compactness, cable productivity, fiber strain induced by cable bending, optical loss characteristics and capacity for mass splicing. As a result, we confirmed the excellence of these cables and their fiber splicing workability.

Casing Pipe Damage Detection with Optical Fiber Sensors: A Case Study in Oil Well Constructions

Casing pipes in oil well constructions may suddenly buckle inward as their inside and outside hydrostatic pressure difference increases. For the safety of construction workers and the steady development of oil industries, it is critically important to measure the stress state of a casing pipe. This study develops a rugged, real-time monitoring, and warning system that combines the distributed Brillouin Scattering Time Domain Reflectometry (BOTDR) and the discrete fiber Bragg grating (FBG) measurement. The BOTDR optical fiber sensors were embedded with no optical fiber splice joints in a fiber-reinforced polymer (FRP) rebar and the FBG sensors were wrapped in epoxy resins and glass clothes, both installed during the segmental construction of casing pipes. In situ tests indicate that the proposed sensing system and installation technique can survive the downhole driving process of casing pipes, withstand a harsh service environment, and remain intact with the casing pipes for compatible strain measurements. The relative error of the measured strains between the distributed and discrete sensors is less than 12%. The FBG sensors successfully measured the maximum horizontal principal stress with a relative error of 6.7% in comparison with a cross multipole array acoustic instrument.