Information Communications Technology,
Civil Engineering Research Section
In late years, optical fiber connecting operations in optical IDF1 (Intermediate Distribution Frame) increases with rapid development of the FTTH (Fiber To The Home). In order to connect optical fibers properly, it is the most important issue in the operation process to carefully and precisely identify targeted line of optical fibers while preventing active line from being mistakenly cut.
In the past, the equipment called an optical fiber identifier2 has been widely used in this operation. In order to sorting the targeted line from various optical fibers in the use of this equipment, at first active lit suspend, and then optical signals for tests, which are called modulated tones, are inserted. Additionally, identifiers are inserted and other complicated operations are needed. Therefore, the operation can have an influence on active line.
In order to solve these problems, at optical IDF operations, we have engaged in developing optical fiber checkers that can identify active line directly.
Fig.1 shows the basic structures of this equipment. The principle of this equipment is to leak a small amount of optical power (we called light leakage) by bending optical fibers, then it (or that) detect the light leakage, and check the line conditions (check active or non-active) The significant characteristic of this equipment is that it can separate optical fiber bending mechanisms, which generate light leakage, into two parts (concave and convex parts) and place independent convex parts (light leakage parts) to optical patch cords. When we check the line condition, we join the concave parts (detecting elements) embedded with PD (photo detector) with light leakage parts as in Fig.2, bend coated fiber at a specified curvature, and detect light leakage. Light leakage parts are held in optical IDF trays as in Fig.3.
Another great function of this equipment is to separate detecting parts for light leakage from reading parts for detecting results. This structure enables us to detect light signals while keeping the increase in bending loss to the minimum when detected. Additionally, miniaturizing detecting parts are realized, and it is expected to improve the workability in narrow spaces. As this equipment doesn't have constant loss unlike integrated tap photo detector, it adapts to existing facilities flexibly, and it has also the advantage of reducing the introduction costs.
Through this experiment, we have confirmed that the minimum received light intensity is less than 40dBm at the light wavelength of 1.31μm/1.55μm, and the insertion loss is less than 1.0dB. We make sure it have not effect on every communications.
The structure of this equipment enables us to see the possibility to develop an optical fiber checker which can detect even in the use of active line with low loss. A patent for this technology has been applied for . We will aim at its lower loss, install it in optical IDF in use on a trial basis, and evaluate the workability for its practical use in the near future.
Fig.1 Basic structure of the optical fiber checker
Fig.2 Monitor device
Fig.3 Inside of the optical IDF tray