Fiber optic measurement system having a reference conductor for controlling the energy level of the light source

A measurement system comprising:

• a reflective surface having a predetermined range of movement;
• a light source which provides light energy;
• a source optical fiber which conducts the light provided by the light source and emits the conducted light to the reflective surface for forming a reflected light beam;
• a reference optical fiber which receives and conducts light of the reflected light beam;
• a controller for receiving the light conducted by the reference fiber and controlling the level of light provided by the light source in response thereto;
• a signal optical fiber located such that the reference fiber is between it and the source fiber, and which receives and conducts light of the reflected light beam and being located such that the amount of light of the reflected light beam conducted varies in accordance with the position of the reflective surface in the predetermined range of movement;
• a characterizer which characterizes the amount of light conducted by the reference fiber over the predetermined range of movement of the reflective surface;
• and
• a processor which receives the characterization from the characterizer and receives the light conducted by the signal fiber and adjusts said light in response to the characterization.

A measurement system comprising:

• a reflective surface having a predetermined range of movement;
• a light source which provides light energy;
• a source optical fiber which conducts the light provided by the light source and emits the conducted light to the reflective surface for forming a reflected light beam;
• a reference optical fiber displaced from the source fiber by a first distance and which receives and conducts light of the reflected light beam and is disposed such that the amount of energy of the reflected beam that it conducts changes relatively little in response to movement of the reflective surface in the predetermined range of movement;
• a controller for receiving the light conducted by the reference fiber and controlling the level of light provided by the light source in response thereto;
• a signal optical fiber displaced from the source fiber by a second distance, the second distance being greater than the first distance, and which receives and conducts light of the reflected light beam and which is disposed such that the amount of energy of the reflected beam that it conducts changes by a relatively large amount in response to movement of the reflective surface in the predetermined range of movement;
• a characterizer which characterizes the amount of light conducted by the reference fiber over the predetermined range of movement of the reflective surface;
• and
• a processor which receives the characterization from the characterizer and receives the light conducted by the signal fiber and adjusts said light in response to the characterization.