# US 10,502,681 B2 · Apparatus and method for measuring concentration of pollutants in water

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- Number: US 10,502,681 B2
- Document ID: US10502681B2
- Status: Granted
- Kind: B2
- Application number: 16/353,084
- Filed: 2019-03-14
- Published: 2019-07-04
- Granted: 2019-12-10
- Earliest claimed: 2016-12-27
- Applicants: Shenzhen University
- Inventors: Peiguang Yan; Hao Chen; Fengfei Xing; Min Zhang
- Web page: https://patentgrep.com/patent/US10502681B2

## CPC

- G01N 21/31: Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)}
- G01N 21/39: using tunable lasers
- G01N 21/552: Attenuated total reflection
- G02B 6/021: {characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape}
- G02F 1/35: Non-linear optics
- H01S 3/0014: {Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003)}
- H01S 3/094003: {the pumped medium being a fibre}
- H01S 3/1028: {by controlling the temperature}
- H01S 3/1061: {using a variable absorption device}
- H01S 3/113: using intracavity saturable absorbers
- H01S 3/115: using intracavity electro-optic devices
- G01N 33/1826: {Organic contamination in water}
- G01N 2021/391: {Intracavity sample}
- H01S 3/06791: {Fibre ring lasers (fibre laser gyrometers G01C19/72)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

The present disclosure provides an apparatus and a method for measuring a concentration of pollutants in water. A passive Q-switched fiber laser outputs an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting it via an evanescent field fiber, and based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change, outputs an output repetition frequency result of the passive Q-switched fiber laser. The method is simple; and the apparatus based on the method is simple in structure and low in cost.

## Claims

### Claim 1

An apparatus for measuring a concentration of pollutants in water, comprising a passive Q-switched fiber laser, an evanescent field fiber and a spectrum apparatus;
wherein the evanescent field fiber is disposed in a laser resonant cavity of the passive Q-switched fiber laser, and the passive Q-switched fiber laser is connected with the spectrum apparatus;
the passive Q-switched fiber laser is configured to output an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting the Q-switched pulse laser signal via the evanescent field fiber;
the passive Q-switched fiber laser is further configured to output an output repetition frequency result of the passive Q-switched fiber laser based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change; and
the spectrum apparatus is configured to display the output repetition frequency result of the passive Q-switched fiber laser.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein the spectrum apparatus is further configured to determine the concentration of the pollutants in the to-be-tested water sample to obtain a measurement result based on a mapping relationship between a preset output repetition frequency of the passive Q-switched fiber laser and the concentration of the pollutants in the water as well as the output repetition frequency result of the passive Q-switched fiber laser, and to display the measurement result.

### Claim 3 (depends on 1)

The apparatus according to claim 1, wherein a cavity structure of the passive Q-switched fiber laser is any one of a ring cavity structure or a linear cavity structure.

### Claim 4

A method for measuring a concentration of pollutants in water, wherein an evanescent field fiber is disposed in a laser resonant cavity of a passive Q-switched fiber laser, the method comprises:
outputting an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting the Q-switched pulse laser signal via the evanescent field fiber; and
based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change, outputting an output repetition frequency result of the passive Q-switched fiber laser to a spectrum apparatus; and
displaying the output repetition frequency result of the passive Q-switched fiber laser by the spectrum apparatus.

### Claim 5 (depends on 4)

The method according to claim 4, further comprising:
determining the concentration of the pollutants in the to-be-tested water sample to obtain a measurement result based on a mapping relationship between a preset output repetition frequency of the passive Q-switched fiber laser and the concentration of the pollutants in the water as well as the output repetition frequency result of the passive Q-switched fiber laser, and displaying the measurement result by the spectrum apparatus.

### Claim 6 (depends on 4)

The method according to claim 4, wherein a cavity structure of the passive Q-switched fiber laser is any one of a ring cavity structure or a linear cavity structure.