sewer pipe inflow and infiltration diagnosis method based on distributed fiber-optic temperature measurement system

A sewer pipe inflow and infiltration diagnosis method based on a distributed fiber-optic temperature measurement system, wherein the distributed fiber-optic temperature measurement system comprises an optical time-domain reflectometer, a data interpretation module, a temperature sensing fiber-optic cable, and a distributed fiber-optic temperature measurement instrument, wherein

• the method comprises the following steps:
• S1:
• transmitting, by the optical time-domain reflectometer, an original optical signal to the temperature sensing fiber-optic cable provided in a sewer pipe;
• S2:
• feeding back, by the temperature sensing fiber-optic cable, a modulated optical signal to the optical time-domain reflectometer due to a temperature effect;
• S3:
• subjecting, by the distributed fiber-optic temperature measurement instrument, the modulated optical signal to photoelectric conversion to acquire binary information characterizing a measurement time, a measured temperature, and a fiber location;
• S4:
• converting, by the data interpretation module, the binary information into decimal information;
• S5:
• drawing a spatiotemporal map of a water temperature inside the sewer pipe based on the decimal information;
• and
• S6:
• eliminating a background noise value in the spatiotemporal map of the water temperature, identifying an abnormal water temperature point, and determining an inflow and infiltration point of the sewer pipe;
• wherein in step S6, the method of eliminating the background noise value in the spatiotemporal map of the water temperature comprises:
• setting a positive background noise value a° C. (a>0), and eliminating the positive background noise value according to a positive background noise value elimination equation below:
• X
• ⁡
• (
• t
• ,
• l
• )
• =
• {
• 1
• ,
• T
• ⁡
• (
• t
• ,
• l
• )
• -
• T
• ⁡
• (
• t
• ,
• l
• -
• 1
• )
• ≥
• a
• 0
• ,
• T
• ⁡
• (
• t
• ,
• l
• )
• -
• T
• ⁡
• (
• t
• ,
• l
• -
• 1
• )
• <
• a
• wherein, t denotes the measurement time;
• l denotes the fiber location;
• X(t,l) denotes a positive response event matrix with elements 0 and 1;
• T(t,l) denotes a water temperature matrix of a temperature measurement point defined by the fiber location l, and T (t,l−1) denotes a water temperature matrix of a temperature measurement point defined by a fiber location l−1;
• setting a negative background noise value b° C., b<0, and eliminating the negative background noise value according to a negative background noise value elimination equation below:
• X
• ′
• (
• t
• ,
• l
• )
• =
• {
• -
• 1
• ,
• T
• ⁡
• (
• t
• ,
• l
• )
• -
• T
• ⁡
• (
• t
• ,
• l
• -
• 1
• )
• ≤
• b
• 0
• ,
• T
• ⁡
• (
• t
• ,
• l
• )
• -
• T
• ⁡
• (
• t
• ,
• l
• -
• 1
• )
• >
• b
• wherein, X′(t,l) denotes a negative response event matrix with elements 0 and −1;
• and
• expressing the spatiotemporal map of the water temperature by 0, −1, and 1 after eliminating the positive background noise value according to the positive background noise value elimination equation and the negative background noise value according to the negative background noise value elimination equation, wherein −1 and 1 denote the abnormal water temperature point and an abnormal discharge time, respectively.