Field-Installable Fusion Splice Connector Yoshinori Iwashita,1 Takahiro Tsuchida,1 Noriyuki Kawanishi,1 Serin Tan,2 Shigeo Takahashi,2 Kazuhiro Takizawa2 Installing optical connectors in a Fiber-To-The-Home (FTTH) network usually involves fieldinstallable connectors employing mechanical splices. However, some FTTH systems require low-reflectance connectors, demanding ease of installation and robustness of the Kevlar-reinforced fiber cord termination. To meet this requirement, Fujikura has developed a field-installable fusion splice connector that is easy to install and is highly reliable. 1. Introduction To meet the increasing volume of data transmission of video and internet services, FTTH service is rapidly increasing, linking telecommunication carriers directly to subscribers using optical fiber. Currently, two methods of terminating fiber cables in the field are available. One method uses a mechanical splice-type field-installable connector 1-5). The other uses a fusion-spliced connector with a terminated pigtail. Each method has its drawbacks. The mechanical splice exhibits poor reflectance loss, while the fused splice requires additional mechanical protection. In either case, strength is compromised. Special skills and experience are required to properly terminate these cables, which can be difficult in the field. Presently, there is an increasing demand from carriers to produce rugged, low back reflectance fieldinstallable splices. To meet this demand, Fujikura has developed a field-installable fusion splice connector with accessories. splice connector. Figure 2 shows the Fujikura fusion splice protection sleeve heater. The specifications for the fusion splice connector and heater are presented Tables 1 and 2. Fig. 2. Tube heater attached to fusion splicer. 2. The connector Figure 1 shows the Fujikura field-installable fusion Table 1. Fusion splice connector specifications. 1. Structural characteristics Connector type SC End face SPC or APC Compatible fiber/cables φ = 3.0 mm and φ = 2.0 mm cord, φ = 0.9 mm fiber 2. Optical characteristics Insertion loss Less than 0.5 dB (SM) Return loss More than 40 dB (SM, SPC) More than 60 dB (SM, APC) Compliance Telcordia GR-326-CORE, JIS C5973(F04) and IEC61754-4 Fig. 1. Fujikura fusion splice connector. 1 Precision Instruments Products Dept. R&D Group 2 Optical Cable System R&D Center 14 Table 2. Heater specifications. 3. A comparison 1. Heating characteristics Applicable sleeve Fusion splice protection sleeve Maximum sleeve length 70 mm Heating time 100 s (φ = 3 mm cord) 2. Structure Dimension 120 mm (W) × 28 mm (D) × 116 (H) mm Weight 400 g Power source DC 12 V input Other functions Automatic tension applying; power backup function (up to 30 s after switching off the power) Kevlar and cord jacket captured in fusion splice protection sleeve Until recently, the replacement and installation of connectors to Kevlar-reinforced cables in the field has been a tedious process. It required precise alignment and placement of protective components prior to splicing and could become labor intensive, proving to be impractical when repairs had to be made quickly and reliably under diverse conditions. The solution to this problem is the Fujikura field-installable fusion connector, which greatly simplifies and improves the strength and reliability of repairs. A comparison between conventional field connectors and the new Fujikura connector is illustrated in Figs. 3 and 4, and Table 3. 4. Fusion connector installation Figure 5 shows a disposable connector plug holder designed to simplify splicing and assembly of the fusion connector to a Kevlar-reinforced cable. Features of this connector plug holder are as follows: Internal structure that takes into consideration ferrule push back Table 3. Comparison of number of parts. Items Fig. 3. Structure of fusion splice connector. [Conventional technology] Conventional Current Housing 1 1 Connector 1 1 Fusion splice sleeve 1 1 Protection tube 1 1 Crimp ring for Kevlar 1 0 Crimp ring for cord jacket 1 0 Boot 1 0 Total no. of parts 7 4 Remarks Fixed by fusion splice sleeve Assembled with protection tube Crimp ring Protection tube [Fujikura fusion connector] Fusion splice protection sleeve Fig. 4. Comparison of parts. Fig. 5. Connector plug holder with connector plug. Fujikura Technical Review, 2008 15 Fig. 6. Fiber transfer device. After splicing optical fiber cord to the fusion connector, the spliced fusion connector has to be transferred to the heater. Bare fiber tends to break easily when removing the spliced fusion connector from the splicer or during the transfer. During normal splicing, only optical fiber is being moved to the heater, but in the case of fusion connector, preset connector plug holder has to be moved to the heater. The fusion splice portion (bare fiber portion) between optical fiber cord and connector holder tends to bend when sufficient tension is not applied, resulting in a lot of stress concentration, and hence breaking of fiber. To resolve this issue, a fiber transfer device as shown in Fig. 6 is developed, enabling easy transfer without affecting the bare fiber. With this fiber transfer device, a stable and reliable splicing process is realized without being influenced by the degree of skill of the operator. 16 wavelength: average: maximum: sample size: 12 1.31 µm / 1.55 µm 0.18dB / 0.16 dB 0.34 dB / 0.34 dB 40 / 40 10 frequency (1) A disposable holder comes with every connector. The connector plug is set into the holder prior to shipping. This simplifies field installation. (2) An assembly compatible with most mass fusion splicing machines that use the fiber holder system. (3) A connector plug holder is so designed that it can be tilted when set into the heater. (4) A hook assembly used to ease the transfer of fiber. Fig. 7. Side pull test with specially designed boot. 8 6 1.31 1.55 4 2 0 0.07 0.11 0.15 0.19 0.23 0.27 0.31 0.35 0.39 insertion loss (dB) Fig. 8. Insertion loss of fusion splice connector. to prevent the optical cord from bending below its minimum permissible bending radius. This specially designed boot is shown in Fig. 7. 6. Characteristics of fusion connector 6.1. Optical characteristics The insertion loss performance of the fusion connector (APC type) against master connector is shown in Fig. 8. Even with two joints, a good average loss of 0.16 dB at 1.55 µm wavelength is obtained. In addition, reflectance of more than 65 dB is achieved. 5. Side pull characteristics 6.2. Mechanical and environmental characteristics Structural design of the fusion splice protection sleeve was optimized to guarantee stable transverse load characteristics such that optical performance of the connector is not adversely affected when a load is applied at 90° to the connector. Transmission with Applied Loads test in Telcordia GR-326-CORE, stipulates that the change in insertion loss during loading is less than 0.5 dB when various loads up to 2 kg are applied at 90° to the connector. To counter this demanding criterion, a strain-relief boot was designed with the most suitable parameters The mechanical and environmental performance of the fusion connector (APC type) is presented in Table 4. Even though the tests, conducted in series in accordance with Telcordia GR-326-CORE, are tedious, good results were obtained, verifying that the connector has high reliability. 7. Conclusion The fusion connector developed has achieved the twin objective of easy installation and high reliability. Also, the accessories developed simultaneoulsy Table 4. Reliability test results of fusion splice connector. Results Test items Criteria Sample size Insertion loss Reflectance [maximum change (dB)] [maximum change (dB)] Wavelength (µm) Wavelength (µm) 1.31 1.55 1.31 1.55 Thermal age test 85 °C, 168 h 15 0.10 0.08 1.7 3.8 Thermal cycle −40 to 75 °C, 21 cycles, 168 h 15 0.15 0.14 1.3 2.9 Humidity age 75 °C, 95%RH, 168 h 15 0.16 0.07 1.6 4.3 Humidity/condensation cycle −10 to 65 °C, 95%RH, 14 cycles, 168 h 15 0.13 0.07 1.7 3.9 Post condensation thermal cycle −40 to 75 °C, 21 cycles, 168 h 15 0.20 0.20 1.7 4.2 Flex test 0.9 kgf, −90° to +90°, 100 cycles (before and after test) 15 0.04 0.07 1.6 2.0 Twist test 1.35 kgf, −900° to +900°, 9 cycles (before and after test) 15 0.03 0.03 0.2 0.4 4.5 kgf, 5 s (before and after test) 15 0.09 0.09 0.1 0.5 6.8 kgf, 5 s (before and after test) 15 0.09 0.08 0.0 0.5 2.3 kgf, 5 s (before and after test) 15 0.10 0.08 0.2 0.5 3.5 kgf, 5 s (before and after test) 15 0.11 0.13 0.2 0.5 Proof test - straight pull Proof test −90° side pull Transmission with applied tensile load 0.25 kgf, 0° (during test) 15 0.02 0.02 0.3 0.4 0.25 kgf, 90° (during test) 15 0.03 0.04 0.5 0.5 0.25 kgf, 135° (during test) 15 0.03 0.05 0.3 0.5 0.5 0.75 kgf, 0° (during test) 15 0.01 0.02 0.3 0.75 kgf, 90° (during test) 15 0.06 0.06 0.2 0.6 1.5 kgf, 0° (during test) 15 0.02 0.01 0.3 0.5 1.5 kgf, 90° (during test) 15 0.09 0.09 0.3 0.5 2.0 kgf, 0° (during test) 15 0.06 0.06 0.1 0.5 2.0 kgf, 90° (during test) 15 0.08 0.08 0.2 0.8 8 impacts from 1.5 m; against concrete block (before and after test) 15 0.08 0.10 1.4 0.2 Durability test 200 times 15 0.16 0.15 2.2 4.1 Vibration test 1.5 mm, 10−55 Hz, 3 axes, 2 h each (before and after test) 15 0.07 0.01 3.5 1.9 Connector installation test Dimension inside box 70 mm 15 0.06 0.06 1.5 1.1 Impact test enable reliable termination process without requiring special skills. 3) K. Takizawa, et al.: Development of New Mechanical Splice References 4) D. Saito, et al.: Development of Field-Installable Optical 1) K. Takizawa, et al.: Field-Installable Connector for Optical Fiber, 47th IWCS, 1998 2) K. Takizawa, et al.: MT-RJ Optical Connector, 48th IWCS, Fujikura Technical Review, 2008 1999 and Field-Installable Connector for FTTH, 52nd IWCS, 2003 Connector for FTTH, 54th IWCS, 2005 5) T. Kobayashi, et al.: Development of Field-Installable Optical Connector for Aerial Closure, 55th IWCS, 2006 17