| 摘要 |
Separate lasers (5,6) with emission wavelengths at 1300 and 1550 nm are provided whose outputs are combined using a single mode optical fibre wavelength multiplexer (7) of tapered coupler format. The combined output is fed to a single mode optical fibre beam splitter (9), also of tapered coupler format, which is constructed to act as a 3dB splitter for both wavelengths. The beam splitter directs light from the lasers into the fibre under test (10) and back-scattered light from the test fibre on to a photodetector (11). - The electrical signal output of photodetector is amplified and sampled in a front end unit (12). The samples are put into digital form by an A to D converter (13). A signal processor (14) functions as a parallel integrator to form a sum of each digital sample produced from the back-scatter signal resulting from the first light pulse with its counterparts produced with succeeding light pulses. The sums are transferred to a memory (15) for relay to a display (16). (1/2) GBAB- GB2179733 B Separate lasers (5,6) with emission wavelengths at 1300 and 1550 nm are provided whose outputs are combined using a single mode optical fibre wavelength multiplexer (7) of tapered coupler format. The combined output is fed to a single mode optical fibre beam splitter (9), also of tapered coupler format, which is constructed to act as a 3dB splitter for both wavelengths. The beam splitter directs light from the lasers into the fibre under test (10) and back-scattered light from the test fibre on to a photodetector (11). - The electrical signal output of photodetector is amplified and sampled in a front end unit (12). The samples are put into digital form by an A to D converter (13). A signal processor (14) functions as a parallel integrator to form a sum of each digital sample produced from the back-scatter signal resulting from the first light pulse with its counterparts produced with succeeding light pulses. The sums are transferred to a memory (15) for relay to a display (16). (6pp Dwg.No 1/2) - GB2179733 B An optical fibre reflectometer provided with a branched single mode optical transmission path that includes a tandem arrangement of first and second single mode optical couplers, wherein the first coupler is constructed to direct into the same output thereof the light from two or more different lasers with different emission wavelengths launched into different inputs thereof, and wherein the second coupled is constructed to function as a plural wavelength beam-splitter affording substantially the same relative coupling between its ports for each of the two laser emission wavelengths. USAB- US4737026 A The optical fibre reflectometer is provided with a branched single mode optical transmission path that includes a tandem arrangement of two single mode optical couplers. The first coupler is constructed to direct into the same output the light from two or more different lasers. The latter have different emission wavelengths launched into different inputs. - The second coupler is constructed to function as a multiple wavelength beam-splitter according for each of the two or more laser emission wavelengths different strengths of coupling while providing equal divisions of power between the outputs of the second coupler.
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