摘要:
On the basis of a known process for the production of a preform for an optical fiber for optical data transmission technology, the productivity of the process for the production of complex refractive index profiles is to be improved by providing a quartz glass substrate tube which exhibits different doping in radial direction, introducing a core glass made of synthetic quartz glass into the substrate tube and covering the substrate tube with a jacket tube. A substrate tube suitable therefor is also being provided which tube requires less core glass material for the production of the preform, whether during the internal deposition or for the core glass rod in the rod-in-tube technique. Regarding the process it is proposed according to the invention that a substrate tube be used which was obtained by vitrification of a porous tube-shaped SiO2 blank, the substrate tube being provided with a core glass layer which is produced in that to the first radial portion of the SiO2 blank there is added before the vitrification a first dopant which increases the refractive index of quartz glass. The substrate tube according to the invention has in the radial direction regions of different doping whereby it incorporates a core glass layer which has a refractive index of at least 1.459.
摘要:
An improved method and apparatus are disclosed for monitoring relative movement between an incident beam of substantially coherent light and a grating on which the beam is directed, wherein light from the beam passing through the grating is sensed by a photodetector, and the cycles in the photodetector output signal are counted. The improvement comprises patterning the beam, transforming the patterned beam into a Fraunhofer diffraction pattern, and further diffracting the Fraunhofer diffraction pattern with the grating to cause an interference image, which is detected by the photodetector. Each two cycles in the output signal of the photodetector then correspond to a relative movement of the beam past one grating period.
摘要:
A large optical preform 303 is made by a modified chemical vapor deposition (MCVD) process by depositing successive layers of core and cladding materials onto the inside surface of a rotating glass tube 33 having a hydroxyl ion (OH.sup.-) level that is less than 0.5 parts per million (ppm) by weight. The tube is then collapsed inwardly to form a core rod 301 in which the deposited core material 31 has a diameter that is greater than about 5 millimeters and the deposited cladding material 32 has an outside diameter that is less than about 15 millimeters. A machine-vision system 140, 150, 160 monitors and controls the diameter of the glass tube by regulating the pressure within the tube. Moreover, the machine-vision system monitors and controls the straightness of the tube by varying its rotational speed according to angular position. After the core rod 301 is formed, it is plasma etched to remove contaminants, and then overclad with two glass jackets 34, 35 having a hydroxyl ion (OH.sup.-) level that is less than 1.0 ppm by weight to create a large preform 303 from which about 400 kilometers of singlemode optical fiber can be drawn per meter of length.