Compact latching-type single-mode-fiber switches fabricated by a fiber-micromachining technique and their practical applications

The design, fabrication, optical and mechanical characteristics, and reliability of several kinds of the latching-type single-mode-fiber (SMF) switch are reported. Practical applications of these switches to optical fiber communication systems and optical testing and sensing systems are also demonstrated. In the developed switches, a movable fiber is actuated by the magnetic attraction force produced between permanent magnets and a micromagnetic-alloy pipe fixed around the fiber. The ultralight micropipes (0.13 (i.d.)-0.18 (o.d.)×5^L mm, 400 μg) were successfully massproduced by a fiber-micromachining technique based on metallizing and etching of sacrificial fibers. We used a refractive-index-matching oil in the switches to reduce insertion loss and reflected light. The several hundred fabricated 1×2 standard SMF switches exhibited excellent optical characteristics, such as typical insertion loss of 0.36 dB, return loss of 49 dB and crosstalk of -70 dB. They exhibited stable latching-type operation with loss changes of below 0.1 dB during 10⁵ switching operations with minimum driving power of 9 mW and switching time of 2 ms. The switches were subjected to endurance (10⁸ switching operations), heat cycles, shock and vibration, and long-term (6.5 years) intermittent operation tests, and revealed no significant optical or mechanical degradation. A 1×8 latching-type SMF switch was constructed using seven 1×2 switches cascaded in three stages and uniform insertion losses of below 0.7 dB and return losses of over 47 dB at each of eight ports were obtained. The 1×2 and 1×8 switches have been applied to NTT´s optical communication systems. We fabricated a compact and cost-effective wavelength switch by installing microfilter chips in the 1×2 switch and confirmed stable latching-type wavelength switching between 1.3- and 1.55-μm optical signals. We also designed and fabricated a polarization-maintaining switch using polarization maintaining and absorption reducing (PANDA) fibers and confirmed stable polarization maintaining switching operations. These switches are applicable not only to optical fiber communication systems, but also to optical testing and sensing systems