Conectronica Revista Maganize industrial de electronica

The German company FOC GmbH that is represented in Spain by Cenvalsa counts on one expanded experience and recognized prestige in the manufacture of optical couplers. In this article basic information is exposed on optical couplers monomode of FOC insisting on its properties, process of manufacture, technology and types of the same.

The optical couplers are used to ramificar or to combine optical signals. They are used in public and private networks of optical fiber to provide a passive distribution and union of points for the optical data transmission (telephone, TV Cable,…. ). Other applications for the optical couplers are measuring equipment, measuring instruments and the technology of sensors.

Features

The fusion couplers make by the called method FBT (Fused Biconical Taper), in which the zones of connection are created by fusion and simultaneous unification of optical fibers. Figure 1 is seen. The basic material is a fiber monoway with a protective coating of acrylato (it castrates primary, typical diameter 250 mm). In order to produce a coupler with two exits, first of everything it is to peel a small portion of protective coating of two optical fibers. The bare zones carefully are cleaned, aligned in parallel and fixed. The process subsequent to the fusion and simultaneous unification allows the passage of the light, or to be reconciled, of a nucleus within the other. Thus, the two fibers form a unique glass connection that is not interrupted by the union, as it would happen in the case of a union to adhesive. The process of fusion and simultaneous unification is controlled by means of a complicated measuring equipment that allows simultaneous measurements, facilitating that the traction process can be interrupted in any point and, thus, to allow that the degree of connection of the signal of entrance within the second fiber or the ratio of connection is controlled (figure 2). After the unification process, the coupler impregnates of a quartz substrate using a special adhesive (figure 3). The substrate with the coupler is inserted in a metallic tube and the ends of the tube are closed with silicone. After this encapsulation, the described coupler has two fibers of entrance and two fibers of exit (= coupler 2x2). By means of a completion without reflection in the second fiber of entrance, we would have a coupler 1x2. The couplers of fusion and modules of couplers with a great number of ports, really make like couplers of fusion or modules of couplers. The fusion couplers really make by fusions and simultaneous unifications of up to 4 fibers (= coupler 1x4). The modules couplers form with a high number of simple couplers., Using these simple couplers and boxes especially developed, a cascade structure is created that provides modules of connection of up to 132 ports (figure 4).

Types of couplers

Manipulating the process of unification and special preliminary treatment of fibers to fuse, couplers with different properties from transmission and connection can be made. The properties of connection of the different types in relation to the wavelength imagine in Figures 5 10. Nm to 1700 are couplers for applications in the rank of wavelengths of telecommunications from 1200 nm, as well as couplers for shorter wave lengh.  For example, in the visual rank. (figure 11).

Couplers monoway POWERSPLITING SSC (Standard Singlemode Couplers). For a wavelength with minimum deviation. For example, 1310 ± 5 nm (figure 5).

WFC (Wavelenght Flattened Couplers). Couplers WFC are couplers in a unique window that it optimizes for a rank of wavelengths and a constant power of ramification is guaranteed traverse of an ample bandwidth. For example 1310 ±40 nm (figure 6). WIC (Wavelenght Independent Couplers). Couplers WIC are couplers in double window that guarantee a constant power of ramification in the second and third window (1310±40 and 1550±40 nm) (figure 7). EIC (Extended Wavelenght Independent Couplers).

Couplers EIC are couplers in double window that guarantee a constant power of extended ramification in second and third window (1310±50 and 1550±75 nm). (figure 8). FIC (Full Range Wavelenght Independent Couplers) Couplers FIC are couplers in triple window that guarantee a constant power of ramification in second, third and fourth window (1310±50 and 1550±100 nm) (figure 9). Couplers WAVELENGHT DIVISION MULTIPLEXER Couplers WDM are used to separate or to combine two or more wavelengths (figure 10). Couplers monoway SHORT WAVELENGHT (Short Wavelenght Couplers)

Couplers SWC are optical elements liabilities that allow to the distribution and combination of optical signals with wavelengths below the wavelengths of the rank of the telecommunications, that is to say 532±5 nm (figure 11). Basic technology As it is possible to be seen in Figure 12, the ratio of connection depends on the length of unification and the wavelength of work. If the unification process pauses in a specific point, a specific ratio of connection is obtained to a wavelength. The point To mark a standard coupler with a ratio of connection from 50% to 1550 nm. If this coupler operates with a wavelength of 1310 nm, the ratio of connection is of approximately the 20%. Point B marks a standard coupler with a ratio of symmetrical connection 1310 nm. Point C marks a coupler in unique window of 1550 nm. In this point flexion, the coupler is highly insensible in return in wavelengths. However, this characteristic is not required that it happens to 100% of connection, therefore one of fibers try by chemical attack or preunification. This qualifies the flexion point to be reduced to 50% (figure 12, point C). Point D shows a coupler double window. In this intersection, the connection is the same for two wavelengths, but asymmetric (approx 10%). Here, also, an intersection with a ratio of asymmetric connection has been obtained fusing two fibers that have been pre-treated of different form (figure 12, point D). The point and shows a specific coupler, the good well-known multiplexer by division of wavelength. In this point, 100% of signal to 1550 nm and 0% of signal to 1310 nm is reconciled. This means that a WDM, as a filter, can separate two wavelengths of such form that each exit carries only one wavelength.

Quality assurance

Each coupler can be identified by its serial number, that is to say, is possible at the same time to identify the parameters of manufacture, the place of work and the material used in each coupler. Each component is put under fatigue tests to assure stability in the long term. At the same time, tests in the long term based on Bellcore, such as humidity storage and dry heat, temperature cycles and mechanical tensions were passed successfully. All the couplers are designed to pass the tests of Telcordia GR-1209-CORE and GR-1221-CORE and specifications IEC. In Table I diverse definitions are expressed calculations and schemes related to the parameters for couplers, modules couplers and multiplexers for division of wavelength. Technological development and own manufacture Couplers FOC make with technology “Fused Biconical Taper”. The principles of FOC in manufacture technology date from years 1985. Then FOC was one of the few companies that owned a technology of development and own manufacture. The development of the manufacture technology, of the tools of manufacture, the automatization and measuring equipment was seen like a total integration from the beginnings. Then FOC had all the knowledge and was able continuously to develop their future technology in line with the demands of the market. In the last years an important number of new components has been created. FOC was the first company that presented/displayed some of them in the market it offered and them to his clients. The production in FOC is computerised and highly automated. On the one hand, this allows him to make products standard of high highly repetitive quality. On the other hand, the technological experience of FOC qualifies to the company to make customizados and then components to organize the production to fulfill the requirements specific of each client. From 1991 great number of fusion couplers they have taken place in industrial conditions on a basic technology that it has virtually not changed. In more than 10 years of use of this technology of manufacture it has demonstrated the high degree of long term stability in multitude of projects of different clients. Among others, the majority of the couplers, that settled within the framework of projects OPAL of Deutsche Telekom in the years from 1993 to 1995, made using technology FOC (then like coupler production of Krone Ag). The couplers based on technology FOC have tried on successfully in 4 continents under the diverse conditions of work. Operators of networks and other clients of more than 20 countries are using FOC couplers. This excellent registry must to the fulfillment of the criteria specified in Bellcore/Telcordia GR-1221-CORE and Bellcore/Telcordia GR-1209-CORE. One always occurs to principle priority to these criteria in the development and production of FOC. Quality and data of the tests From the beginning until today the extensive tests for the monitoring and certification of the quality are realised in parallel with the manufacture. FOC has individual tests and launching of clients available. The first tests of accomplishment and effectiveness that were realised in the FOC couplers date from before 1992. The last published test is of the 2006. These also have an extract of the results summarized in Qualification detail and Test Report (QTR). FOC realises east test report to all clients. In the last 10 years the exigencies as well as the products and tests have evolved. In order to satisfy these requirements FOC it has designed the tests to fulfill recognition international IEC from the beginning Standard. This allows the client to make comparisons and logics simple. Today the manufacture of FOC is based on a consistent system of management of the quality ISO that was created in the times in which it was depended on the matrix Diamond GmbH. Thus FOC is able to fulfill a high quality level and to draw up the parameters of manufacture, materials and production with the experience of 10 years. Ample product range FOC offers an ample product range. Thus, almost all the types of couplers are available from a provider:  Couplers monoway and multiway.  dependent and independent Couplers of the wavelength.  Couplers power-splitting and multiplesores (WDM).  symmetrical and asymmetric Couplers.  Couplers directly fused with 2, 3 and 4 fibers and modules couplers.  Couplers for wavelengths of telecommunication and couplers for special wavelengths (couplers of short wavelength).  Attenuators.  Couplers for transmission of signal and transmission of power. However, the product range FOC is not limited components based on the technology of the coupler. FOC also in line mounts connectors with all the norms required in the market, and makes and sells surrounding equipment of distribution and. Thus FOC can provide all the passive lines, transmission and equipment. The FOC components represent additional advantages like:  Less losses of insertion of the component optimizing the adjustment of the thermal coefficient of expansion of all the materials used to the coefficient of expansion of the optical fiber.  Prevention of early failure by exhibition of all the components during 24 hours to a thermal shock before taking the measures.  Chequeo of measures and guarantee of the optical characteristics on the wavelengths specified by the client.  mechanical high resistance and heat capacity by strict pursuit of the predetermined points of rupture, secured using the process of manufacture adapted to the fiber and manufacture of components in line, that is to say, without intermediate connections, means or similar. In the improbable case of a defect FOC additionally it guarantees immediate service and fast replacement of the guaranteed parts and offers fast delivery.