# US 5,708,265 A · Optical power meter using low-power measurement circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,265 A - Document ID: US5708265A - Status: Granted - Kind: A - Application number: 08/777,580 - Filed: 1996-12-31 - Granted: 1998-01-13 - Earliest claimed: 1995-05-11 - Inventors: Craig D. Poole - Web page: https://patentgrep.com/patent/US5708265A ## CPC - G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) ## Abstract A battery or solar-powered apparatus for measuring and displaying optical power transmitted through an optical fiber. The apparatus has a measuring circuit comprising an optical detector (602), a current/voltage converter (704) and a control circuit (702) which provides timing signals and controls the power applied to the measuring circuit. The apparatus is secured within a housing (102) and is sufficiently small and light such that permanent, in-line attachment to the optical fiber is possible. In a first embodiment, a voltage proportional to the measured optical power is available at an output jack (214) attached to the housing (102). The jack further comprises a switch (1760) which enables power to the apparatus during a measurement period. An alternative embodiment comprises an analog/digital converter (1202) which provides a digital representation of the measured optical power. Low-power displays, such as liquid crystal displays (112, 312), provide direct visual output of the digitized representation of the measured optical power, selectably in units of dBm/dB. ## Claims ### Claim 1 Apparatus for in-line measurement of optical power comprising: a housing; an input optical assembly attached to the housing and adapted to be placed in optical communication with an externally situated optical fiber; an optical tap contained within the housing and in optical communication with input optical assembly; an optical detection circuit, having an optical detector, contained within the housing and in optical communication with the optical tap such that optical energy carried by the input optical assembly and tapped off by the optical tap is subsequently detected by the optical detector, said optical detection circuit producing, in response to detected optical energy, a signal which represents a measurement of optical power carried through an output optical assembly; the output optical assembly attached to the housing and in optical communication with the optical tap; and wherein optical power exiting the output optical assembly is greater than or equal to 50% of the optical power carried by the input optical assembly. ### Claim 2 (depends on 1) The apparatus in claim 1 wherein the total mass of said housing, said optical tap and said optical detector is less than 120 grams. ### Claim 3 (depends on 1) The apparatus in claim 1 wherein said apparatus further comprises an optical fiber internally situated within the housing and extending between said input and output optical assemblies, and the optical tap is formed by introducing a permanent microbend in the internally situated optical fiber. ### Claim 4 (depends on 3) The apparatus in claim 3 wherein the microbend has a bend radius of less than 2 mm. ### Claim 5 (depends on 3) The apparatus in claim 3 wherein the internally situated optical fiber also extends through and is common to both of said input and output optical assemblies. ### Claim 6 (depends on 5) The apparatus in claim 5 wherein the microbend has a bend radius of less than 2 mm. ### Claim 7 (depends on 1) The apparatus in claim 1 wherein said optical detector further comprises an optical filter, positioned in an optical path between said optical tap and said optical detector. ### Claim 8 (depends on 1) The apparatus in claim 1 wherein the optical detection circuit further comprises a circuit, contained within the housing, for converting said signal into a digital representation of the optical power measurement. ### Claim 9 (depends on 8) The apparatus in claim 8 further comprising a visual display in electrical communication with the converting circuit for providing a numerical indication of the optical power measurement. ### Claim 10 Apparatus for in-line measurement of optical power comprising: a housing; an input optical assembly attached to the housing and adapted to be placed in optical communication with an externally situated optical fiber; an optical tap contained within the housing and in optical communication with input optical assembly; an optical detection circuit, having an optical detector, contained within the housing and in optical communication with the optical tap such that optical energy carried by the input optical assembly and tapped off by the optical tap is subsequently detected by the optical detector, said optical detection circuit producing a signal in response to detected optical energy so as to provide a measurement of optical power carried through an output optical assembly; and the output optical assembly attached to the housing and in optical communication with the optical tap; wherein the apparatus further comprises: an optical fiber internally situated within the housing and extending between said input and output optical assemblies, and the optical tap is formed by introducing a permanent microbend in the internally situated optical fiber. ### Claim 11 (depends on 10) The apparatus in claim 10 wherein the total mass of said housing, said optical tap and said optical detector is less than 120 grams. ### Claim 12 (depends on 10) The apparatus in claim 10 wherein the microbend has a bend radius of less than 2 mm. ### Claim 13 (depends on 10) The apparatus in claim 10 wherein the internally situated optical fiber also extends through and is common to both of said input and output optical assemblies. ### Claim 14 (depends on 13) The apparatus in claim 13 wherein the microbend has a bend radius of less than 2 mm. ### Claim 15 (depends on 10) The apparatus in claim 10 wherein said optical detector further comprises an optical filter, positioned in an optical path between said optical tap and said optical detector. ### Claim 16 (depends on 10) The apparatus in claim 10 wherein the optical detection circuit further comprises a circuit, contained within the housing, for converting said signal into a digital representation of the optical power measurement. ### Claim 17 (depends on 16) The apparatus in claim 16 further comprising a visual display in electrical communication with the converting circuit for providing a numerical indication of the optical power measurement. ### Claim 18 Apparatus for in-line measurement of optical power comprising: a housing; an input optical assembly attached to the housing and adapted to be placed in optical communication with an externally situated optical fiber; an optical tap contained within the housing and in optical communication with input optical assembly; an optical detection circuit, having an optical detector, contained within the housing and in optical communication with the optical tap such that optical energy carried by the input optical assembly and tapped off by the optical tap is subsequently detected by the optical detector, said optical detection circuit producing, in response to detected optical energy, a signal which represents a measurement of optical power carried through an output optical assembly; and the output optical assembly attached to the housing and in optical communication with the optical tap; wherein the total mass of the housing, the optical tap and the optical detector is less than 120 grams. ### Claim 19 (depends on 18) The apparatus in claim 18 wherein said apparatus further comprises an optical fiber internally situated within the housing and extending between said input and output optical assemblies, and the optical tap is formed by introducing a permanent microbend in the internally situated optical fiber. ### Claim 20 (depends on 19) The apparatus in claim 19 wherein the microbend has a bend radius of less than 2 mm. ### Claim 21 (depends on 19) The apparatus in claim 19 wherein the internally situated optical fiber also extends through and is common to both of said input and output optical assemblies. ### Claim 22 (depends on 21) The apparatus in claim 21 wherein the microbend has a bend radius of less than 2 mm. ### Claim 23 (depends on 18) The apparatus in claim 18 wherein said optical detector further comprises an optical filter, positioned in an optical path between said optical tap and said optical detector. ### Claim 24 (depends on 18) The apparatus in claim 18 wherein the optical detection circuit further comprises a circuit, contained within the housing, for converting said signal into a digital representation of the optical power measurement. ### Claim 25 (depends on 24) The apparatus in claim 24 further comprising a visual display in electrical communication with the converting circuit for providing a numerical indication of the optical power measurement. ### Claim 26 Low-power apparatus for sensing and displaying optical power comprising: a housing; a power source contained within the housing; a measuring circuit contained within the housing, said measuring circuit having an optical detector and producing a signal in response to and related to optical power sensed by the optical detector; and a control circuit contained within the housing and electrically connected to said measuring circuit, said control circuit comprising: i) a timing circuit for producing a first periodic voltage signal; and ii) an electrically controlled switch, responsive to said periodic voltage signal and connected to the power source for applying electrical power therefrom to said measuring circuit so as to successively energize the measuring circuit; wherein said power source is one selected from the group consisting of a battery and a solar cell. ### Claim 27 (depends on 26) The apparatus in claim 26 wherein the measuring circuit further comprises a current/voltage converter in electrical communication with the optical detector, said current/voltage converter producing a first voltage related to said optical power. ### Claim 28 (depends on 27) The apparatus in claim 27 further comprising a settling circuit in electrical communication with said current/voltage converter and said control circuit such that the settling circuit produces an intermittent current in said current/voltage converter in response to said periodic voltage signal from said control circuit, wherein a time duration of said intermittent current is less than a time duration during which said electrically controlled switch is closed. ### Claim 29 (depends on 28) The apparatus in claim 28 wherein said settling circuit comprises a capacitor and resistor. ### Claim 30 (depends on 27) The apparatus in claim 27 wherein said current/voltage converter is one selected from the group consisting of a transistor and a diode. ### Claim 31 (depends on 27) The apparatus in claim 27 further comprising an output jack, in electrical communication with said current/voltage converter such that said first voltage is present at said jack. ### Claim 32 (depends on 31) The apparatus in claim 31 wherein said output jack further comprises a power switch in electrical communication with said power source such that electrical power is applied to said measuring circuit and said control circuit when a mated plug is inserted into the output jack.