Device for tapping scattered light from a joint in an adjustable connector for two optical fibre waveguides

In an optical fibre communication system including a transmitter having an optical signal output and an optical control signal input for regulating the signal level of the output apparatus comprising:

• a first optical fibre waveguide connected to the signal output of the transmitter;
• a second optical waveguide;
• and optical waveguide connecting means comprising a first cylindrical jointing tube disposed about said first optical fibre waveguide;
• a second cylindrical jointing tube disposed about said second optical fibre waveguide;
• a jointing sleeve disposed about said jointing tubes and rotatably receiving the same;
• a capillary cylindrical tube of transparent material disposed about said second optical fibre waveguide, adjustable connector means connecting said jointing tubes in said jointing sleeve to permit relative rotation of said jointing tubes for adjusting eccentricity of said fiber waveguides, the capillary tube having an oblique angled surface at the end which is remote from the joint for laterally projecting scattered light propagated from the joint;
• said jointing tube surrounding said capillary tube being provided with a side window for accessing laterally projected light;
• and means for coupling the laterally projected light to the optical control signal input of the transmitter.