Telefonaktiebolaget Lm Ericsson (publ)

Ellef Hersoug

Wei-Ping Huang

Tomas Adeback

Kjell Ahlstedt

Christian Gottlicher Palafox

In the manufacture of an optical attenuator having a desired value of the optical loss end regions of two optical fibers are placed with an offset in the traverse direction in relation to each other and having their end surface at each other. Thereafter the region at end surfaces is heated to make the ends melt to each other and the heating is then further continued. To achieve the desired loss in the finished attenuating splice the further heating is stopped for an optical loss exceeding the desired loss by a calculated value. This value can be obtained from measurements in real time of the loss for the splice during the continued heating. The measurements can be made at the beginning and end of an interrupt of the further heating. An attenuator manufactured in this way obtains an attenuation that accurately agrees with the desired value.

Optical attenuator and method of manufacture

The present invention relates to a method for accurately calibrating fusion temperature in optical fiber splicing. With assistance of direct arc-recentering technique, two optical fibers are spliced and then continuously heated with a post-fusion process. In the process, the fusion temperature is automatically determined in terms of effective fusion currents, which is done by real-time monitoring the fusion time dependence of cladding diameter reduction. In comparison with model calculations, variations of fusion temperature caused by changes of electrode condition and operating environment, e.g. altitude, temperature and humidity are derived. To recover the optimal fusion temperature in various fusion processes, the calibrating results are automatically invoked to compensate fusion currents.

Fusion temperature calibration

Optical fibers (') are fusion spliced to each other by using a CO2 laser () having an emission wavelength of 9.3 microm. The heat absorption of the fibers is higher and the variation of the absorption for small deviations of the wavelength is smaller than at the conventional wavelength of 10.6 microm. As a result, less laser power is needed, the laser construction may be more compact and safety problems can easier be handled. The optical arrangement for the light beam of the CO2 laser includes deflecting and focusing the collimated laser beam () emitted by the laser using a mirror () having a curved surface of concave nearly paraboloid shape, the splice position () located at a small distance of the focus of the mirror and well outside the collimated beam.

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Stockholm, Sweden

Ellef Hersoug