Apparatus for measuring the incident power of light in fiber optics

• US 4,012,955 A
• Filed: 01/19/1976
• Issued: 03/22/1977
• Est. Priority Date: 01/19/1976
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Szente, Pedro Americo
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US05/650,404
• Time in Patent Office: 428 Days
• Field of Search: 73/190 EW, 73/355, 250/227
• US Class Current: 374/32
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: G01K 17/003 for measuring the power of light beams, e.g. laser beams

Abstract

A power measuring apparatus for measuring the incident power of light transmitted through a fiber optic light conductor comprises a first thermistor optically coupled to a fiber optic light conductor. The first thermistor forms one arm of a self-balancing resistance bridge. A second thermistor, physically close to the first thermistor but isolated from the light incident on the first thermistor, is connected to a second self-balancing bridge. The outputs of the self-balancing bridges are connected to metering circuitry which provides a measure of the incident power.

Claims

1. An apparatus for measuring the incident power of light from a fiber optic light conductor comprising:

a first fiber optic light conductor for receiving light;

a measurement thermistor which has first and second electrical leads and which is bonded to an end of the first fiber optic light conductor with an optically transparent bonding agent;

a second fiber optic light conductor which receives no light;

a reference thermistor which has first and second electrical leads and which is bonded to an end of the second fiber optic light conductor; and

electrical connection means for providing electrical connection to the measurement and reference thermistors and adapted to be connected to metering apparatus to provide an indication of the incident power of the light transmitted through the first fiber optic light conductor to the measurement thermistor, the electrical connection means including electrically conductive terminals to which the first and second leads of the measurement and reference thermistors are attached.

2. An apparatus as in claim 1 further comprising a housing enclosing the measurement thermistor and the reference thermistor and attached to the electrical connection means.

3. An apparatus as in claim 2 further comprising:

a septum supported within the housing for separating the measurement thermistor and the reference thermistor.

4. An apparatus as in claim 2 wherein the housing includes a base with feed-through insulators for supporting and electrically insulating each of the electrically conductive terminals, with a feed-through insulator for supporting and thermally isolating the first fiber optic light conductor, and with a mounting insulator for supporting and thermally isolating the second fiber optic light conductor.

5. An apparatus as in claim 4 further comprising optical connection means attached to the first fiber optic light conductor for receiving light from a fiber optic cable.

6. An apparatus as in claim 4 further comprising metering apparatus connected to the electrical connection means for measuring the resistance of the measurement thermistor.

7. An apparatus as in claim 6 wherein the metering apparatus comprises a test self-balancing bridge and a reference self-balancing bridge, one arm of the test self-balancing bridge including the measurement thermistor and one arm of the reference self-balancing bridge including the reference thermistor.

8. An apparatus as in claim 4 including a heat sink member thermally coupled to, but electrically insulated from, the housing and the electrically conductive terminals and thermally insulated from the first fiber optic light conductor.

9. An apparatus as in claim 1 wherein the measurement thermistor is at least as large as the cross section of the first fiber optic light conductor at the point where the measurement thermistor is bonded thereto.