OPTICAL POWER MEASUREMENT DEVICE
An optical power meter including a mechanical interface that establishes a predetermined air gap, while avoiding physical contact with the sensitive area of the DUT. The mechanical interface is formed such that the test instrument contacts the DUT in the non-sensitive region over an area large enough to establish contact pressure that is well within the strength of the DUT's material. Accordingly, the non-contacting optical element enables optical power to be collected and relayed with a quantifiable and repeatable power loss. A high-NA, large area optical element is used to collect and relay optical power accurately while maintaining low sensitivity to axial or radial alignment.
1 . An optical power measurement device for measuring optical power of a source of light from a device under test (DUT) comprising:
a test instrument having a longitudinal optical axis and comprising:
an optical element for transmitting test light, formed from at least a portion of the source of light; and
a ferrule surrounding the optical element; and
a photodetector for measuring the test light optically coupled to the optical element;
wherein the ferrule includes:
a first contact surface for abutting against a second contact surface on the DUT, parallel to the first contact surface, and
a non-contact surface spaced from an optically transmitting area of the DUT by an air gap when the first and second contact surfaces are abutting, the non-contact surface including an optically receptive area formed by an end of the optical element for receiving the test light from an optically transmitting area of the DUT.
2 . The device of claim 1 , wherein the first contact surface is at an angle with the non-contact surface, forming an acute angle between the optically transmitting area and the optically receptive area.
3 . The device of claim 2 , wherein the acute angle is between 5° and 15°.
4 . The device of claim 2 , wherein the non-contact surface is perpendicular to the longitudinal optical axis of the test instrument; and
wherein the first contact surface slopes away from the non-contact surface, parallel to an angled end face of the DUT, forming the acute angle between the optically transmitting area and the optically receptive area.
5 . The device of claim 2 , wherein the first contact surface is perpendicular to the longitudinal optical axis of the test instrument, and
wherein the non-contact surface slopes away from the first contact surface, parallel to a flat end face of the DUT, forming the acute angle between the optically transmitting area and the optically receptive area.
6 . The device of claim 1 , wherein the non-contact surface is defined by a groove in the end of the ferrule.
7 . The device of claim 6 , wherein the groove includes a concave lower face.
8 . The device of claim 6 , wherein the groove is circular-shaped surrounding the optically receptive area; and wherein the non-contact area comprises a annular-shaped area surrounding the circular-shaped groove.
9 . The device of claim 1 , wherein the air gap has a constant length of between 10 and 25 microns across.
10 . The device of claim 1 , wherein the optically receptive area of the optical element has an NA at least 2× higher than the optically transmitting area of the DUT.
11 . The device of claim 1 , wherein the optically receptive area of the optical element has a diameter at least 5× larger than the optically transmitting area of the DUT.
12 . The device of claim 1 , wherein the optical element comprises an optical fiber.
13 . The device of claim 12 , wherein the optical fiber has a NA greater than 0.3 and a core diameter of at least 200 um.
14 . The device of claim 1 , wherein the optical element comprises a ball lens, and an optical fiber.
15 . The device of claim 1 , wherein the optical element comprises a plurality of relay lenses.
16 . The device of claim 1 , wherein the optical element comprises a grin lens.
17 . An optical power measurement device for measuring optical power of a source of light from a device under test (DUT) comprising:
a test instrument having a longitudinal optical axis and including a ferrule; and
a photodetector mounted within the ferrule for measuring test light, formed from at least a portion of the source of light;
wherein the ferrule includes:
a first contact surface for abutting against a second contact surface on the DUT, parallel to the first contact surface, and
a non-contact surface spaced from an optically transmitting area of the DUT by an air gap when the first and second contact surfaces are abutting, the non-contact surface including an optically receptive area formed by an end of the optical element for receiving the test light from an optically transmitting area of the DUT.
18 . The device of claim 17 , wherein the first contact surface is at an angle with the non-contact surface, forming an acute angle between the optically transmitting area and the optically receptive area.
19 . The device of claim 18 , wherein the acute angle is between 5° and 15°.
20 . The device of claim 17 , wherein optical receptive area of the optical element has a diameter at least 5× larger than the optically transmitting area of the DUT.