CN107270952B - Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection - Google Patents
Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection Download PDFInfo
- Publication number
- CN107270952B CN107270952B CN201710624875.2A CN201710624875A CN107270952B CN 107270952 B CN107270952 B CN 107270952B CN 201710624875 A CN201710624875 A CN 201710624875A CN 107270952 B CN107270952 B CN 107270952B
- Authority
- CN
- China
- Prior art keywords
- disturbance
- distance
- noise reduction
- optical fiber
- frequency domain
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 22
- 230000003287 optical effect Effects 0.000 title claims abstract description 21
- 238000003672 processing method Methods 0.000 title claims abstract description 9
- 238000000034 method Methods 0.000 claims abstract description 24
- 230000009467 reduction Effects 0.000 claims abstract description 17
- 238000012545 processing Methods 0.000 claims abstract description 14
- 238000001914 filtration Methods 0.000 claims abstract description 10
- 238000005728 strengthening Methods 0.000 claims abstract description 3
- 238000005259 measurement Methods 0.000 claims abstract 2
- 230000035559 beat frequency Effects 0.000 claims description 7
- 238000004458 analytical method Methods 0.000 claims description 6
- 230000009466 transformation Effects 0.000 claims description 6
- 238000012935 Averaging Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 claims description 3
- 230000002194 synthesizing effect Effects 0.000 claims description 3
- 230000008859 change Effects 0.000 description 3
- 230000007123 defense Effects 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
The invention provides a method for processing a distributed disturbance sensing signal based on an optical frequency domain reflection long-distance optical fiber, and S1, an image processing method is utilized to perform noise reduction and strengthening characteristic processing on a measurement signal; s2, adopting a noise reduction method without spatial resolution loss and using low-pass filtering to reduce noise, and under the condition of ensuring spatial resolution, enabling the disturbance position to be more obvious and distinguishing multipoint disturbance. The method for processing the distributed disturbance sensing signal based on the optical frequency domain reflection long-distance optical fiber effectively reduces noise and reserves disturbance characteristic information by using an image processing method. When multi-point disturbance is resolved, the noise reduction method without spatial resolution loss utilizes low-pass filtering noise reduction to enable the disturbance position to be more obvious under the condition of ensuring the spatial resolution.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensors, and particularly relates to a method for processing a long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflection.
Background
The long-distance distributed disturbance sensing is widely applied to the fields of civil life, national defense safety and the like, such as the structural health monitoring of important parts of aircrafts, spacecrafts, ships, national defense equipment, industrial equipment, bridge culverts and the like, and the high-precision high-spatial-resolution long-distance distributed disturbance sensing can be realized by utilizing the Rayleigh scattering spectral movement of single-mode optical fibers in the reflection of the optical frequency domain.
However, in the existing optical fiber disturbance sensing based on optical frequency domain reflection, the problems that the multipoint disturbance positions cannot be distinguished, the noise of sensing signals is large, the spatial resolution is low and the like exist mostly.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for processing a long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflection, so as to overcome the problems that in the existing optical fiber disturbance sensing based on optical frequency domain reflection, the multi-point disturbance positions cannot be distinguished, the noise of a sensing signal is large, and the spatial resolution is low.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection, S1, using image processing method to make noise reduction and strengthening feature processing for the measured signal;
s2, adopting a noise reduction method without spatial resolution loss and using low-pass filtering to reduce noise, and under the condition of ensuring spatial resolution, enabling the disturbance position to be more obvious and distinguishing multipoint disturbance.
Further, the execution method of step S1 is specifically as follows:
s101, forming beat frequency interference signals by optical fiber back Rayleigh scattering in a main interferometer of the optical frequency domain reflectometer;
s102, segmenting the beat frequency interference signal along a time axis, and respectively carrying out fast Fourier transform;
s103, using a time-frequency analysis method to set the signals into an image by taking time and distance as axes;
and S104, performing noise reduction on the image by using a local mean filtering method, averaging time domain information corresponding to each position, and synthesizing a path of distance domain information.
Further, the method for resolving the multi-point disturbance specifically includes:
and carrying out Fourier transformation on the distance domain signal, setting the high-frequency information to zero, carrying out inverse transformation to the distance domain to obtain a low-pass noise reduction effect, searching a concave trough in the processed backward Rayleigh scattering distance domain signal, wherein the position of the concave trough is the second point disturbance position, and distinguishing the multi-point disturbance by the method.
Compared with the prior art, the optical frequency domain reflection-based long-distance optical fiber distributed disturbance sensing signal processing method has the following advantages:
the method for processing the distributed disturbance sensing signal based on the optical frequency domain reflection long-distance optical fiber effectively reduces noise and reserves disturbance characteristic information by using an image processing method. When multi-point disturbance is resolved, the noise reduction method without spatial resolution loss utilizes low-pass filtering noise reduction to enable the disturbance position to be more obvious under the condition of ensuring the spatial resolution.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic flow chart of a method for processing a long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflection according to an embodiment of the present invention;
FIG. 2 is an analysis image for time-frequency analysis;
FIG. 3 is a diagram of the results after denoising.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
As shown in fig. 1, the method for processing the distributed disturbance sensing signal based on the optical frequency domain reflection long-distance optical fiber comprises the following specific steps:
(1) forming beat frequency interference signals by optical fiber back Rayleigh scattering in a main interferometer of the optical frequency domain reflectometer, segmenting the beat frequency interference signals along a time axis, respectively carrying out fast Fourier transform, and grouping the signals by taking time and distance as axes as images by a time-frequency analysis method;
(2) carrying out noise reduction processing on the image by using a local mean filtering method, averaging time domain information corresponding to each position, and synthesizing into a path of distance domain information;
(3) and aiming at multi-point disturbance, carrying out Fourier transformation on the distance domain signal, setting the high-frequency information to be zero, and carrying out inverse transformation to the distance domain to obtain a low-pass noise reduction effect. And searching a concave trough in the processed backward Rayleigh scattering distance domain signal, wherein the position of the concave trough is the second point disturbance position, and distinguishing the multi-point disturbance by the method.
The system adopted comprises: GPIB control module, computer, main interferometer, additional interferometer, collection system, tunable light source. The main interferometer is the core of the optical frequency domain reflectometer, and is a modified Mach Zehnder interferometer.
The working principle of the system is as follows:
when the device works, the computer controls the tunable laser to control the tuning speed, the central wavelength, the tuning start and the like through the GPIB control module; the emergent light of the tunable laser is received by the acquisition device which transmits the acquired analog electrical signal to the computer by sensing optical fiber disturbance information and outputting signal light by the optical frequency domain reflectometer.
The principle of disturbance sensing is that, assuming a disturbance event exists at a certain position in the optical fiber to be tested, its vibration causes the phase change of the test optical field E in the test arm and the change of the loss reflectivity R. The vibration induced phase change can be expressed as:
Δφ＝δsin(2πf_m t)
where f _ m is the vibration frequency and δ is the modulation amplitude of the phase. The loss reflectivity is also attenuated by the vibration, resulting in the reduction of the amplitude of the range domain signal. The novel algorithm for measuring multipoint disturbance by long-distance optical fiber distributed sensing is characterized in that the principle characteristics are utilized to detect the disturbance position.
The principle of image processing for time-frequency analysis of disturbance signals is that beat frequency interference signals are segmented along a time axis and are subjected to fast Fourier transform respectively, so that two-dimensional signals with double variables of time and frequency are formed, and the two-dimensional signals are used as images to be processed. And by using a local mean filtering method, the noise of the sensing signal is effectively reduced, and disturbance characteristic information is reserved.
As shown in fig. 2, the two-dimensional image with time and distance as horizontal and vertical coordinates is shown, and the upper image is the processed image with local mean filtering in the lower image, so that the visible noise is significantly suppressed. As shown in fig. 3, is a range domain image restored after processing.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (1)
1. The method for processing the long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflection is characterized by comprising the following steps of:
s1, carrying out noise reduction strengthening characteristic processing on the measurement signal by using an image processing method;
s2, adopting a noise reduction method without spatial resolution loss and using low-pass filtering to reduce noise, and under the condition of ensuring spatial resolution, enabling the disturbance position to be more obvious and distinguishing multipoint disturbance;
the execution method of step S1 is specifically as follows:
s101, forming beat frequency interference signals by optical fiber back Rayleigh scattering in a main interferometer of the optical frequency domain reflectometer;
s102, segmenting the beat frequency interference signal along a time axis, and respectively carrying out fast Fourier transform;
s103, forming an image by using the signals with time and distance as axes by using a time-frequency analysis method;
s104, performing noise reduction on the image by using a local mean filtering method, averaging time domain information corresponding to each position, and synthesizing a path of distance domain information;
the method for resolving the multi-point disturbance specifically comprises the following steps:
and carrying out Fourier transformation on the distance domain signal, setting the high-frequency information to zero, carrying out inverse transformation to the distance domain to obtain a low-pass noise reduction effect, searching a concave trough in the processed backward Rayleigh scattering distance domain signal, wherein the position of the concave trough is the second point disturbance position, and distinguishing the multi-point disturbance by the method.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710624875.2A CN107270952B (en) | 2017-07-27 | 2017-07-27 | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection |
| PCT/CN2018/084568 WO2019019735A1 (en) | 2017-07-27 | 2018-04-26 | Method for processing long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710624875.2A CN107270952B (en) | 2017-07-27 | 2017-07-27 | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107270952A CN107270952A (en) | 2017-10-20 |
| CN107270952B true CN107270952B (en) | 2020-03-31 |
Family
ID=60079295
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710624875.2A Active CN107270952B (en) | 2017-07-27 | 2017-07-27 | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN107270952B (en) |
| WO (1) | WO2019019735A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107270952B (en) * | 2017-07-27 | 2020-03-31 | 天津求实飞博科技有限公司 | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection |
| CN110160569B (en) * | 2019-04-24 | 2021-09-24 | 国网浙江省电力有限公司信息通信分公司 | Noise reduction method and system for distributed optical fiber sensing signal and storage medium |
| CN111579048B (en) * | 2020-05-12 | 2021-07-16 | 山东大学 | OFDR system vibration detection method based on sliding time gating |
| WO2022000333A1 (en) * | 2020-06-30 | 2022-01-06 | 华为技术有限公司 | Radar detection method and related device |
| CN113237431B (en) * | 2021-05-06 | 2022-03-18 | 山东大学 | Measurement method for improving distributed spatial resolution of OFDR system |
| CN113188461B (en) * | 2021-05-06 | 2022-05-17 | 山东大学 | OFDR large strain measurement method under high spatial resolution |
| CN116399379B (en) * | 2023-06-07 | 2023-11-03 | 山东省科学院激光研究所 | Distributed optical fiber acoustic wave sensing system and measuring method thereof |
| CN116380140B (en) * | 2023-06-07 | 2023-11-03 | 山东省科学院激光研究所 | Distributed acoustic wave sensing system based on mean value filtering technology and measuring method thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003029851A2 (en) * | 2001-09-28 | 2003-04-10 | University Of Southampton | Optical fibre-based devices utilising the raman effect |
| CN102589587A (en) * | 2012-02-13 | 2012-07-18 | 上海大学 | Improved short-term cross-correlation positioning method for chaos fiber fence system |
| CN104215271A (en) * | 2014-07-30 | 2014-12-17 | 复旦大学 | Positioning method for disturbance position in distributed optical fiber disturbance monitoring system |
| CN106872071A (en) * | 2016-12-30 | 2017-06-20 | 江苏骏龙光电科技股份有限公司 | A kind of temp measuring method based on optical frequency domain reflection technology |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4976507A (en) * | 1988-06-20 | 1990-12-11 | Mcdonnell Douglas Corporation | Sagnac distributed sensor |
| CN102322880B (en) * | 2011-08-18 | 2013-06-05 | 天津大学 | Polarization sensitive distributive optical frequency domain reflection disturbance sensor and demodulation method |
| CN102401667B (en) * | 2011-09-29 | 2016-03-30 | 北京航空航天大学 | There is optical fiber distributed perturbation method for sensing and the system of disturbance character recognition function |
| CN102506913B (en) * | 2011-10-28 | 2015-04-08 | 北京航空航天大学 | Interference type optical fiber distribution disturbance sensor and disturbance location method thereof |
| CN103090961B (en) * | 2013-02-01 | 2014-11-26 | 华中科技大学 | Disturbance source positioning method of distributed type optical fiber sensing system |
| US9632006B2 (en) * | 2013-06-10 | 2017-04-25 | General Photonics Corporation | Distributed fiber bend and stress measurement for determining optical fiber reliability by multi-wavelength optical reflectometry |
| CN104240455B (en) * | 2014-08-07 | 2016-08-17 | 北京航天控制仪器研究所 | A kind of disturbance event recognition methods in distribution type fiber-optic pipeline safety early warning system |
| CN104729667B (en) * | 2015-03-25 | 2017-11-07 | 北京航天控制仪器研究所 | A kind of disturbance kind identification method in distributed optical fiber vibration sensing system |
| CN105277272A (en) * | 2015-10-25 | 2016-01-27 | 复旦大学 | Distributed optical fiber vibration sensing multi-point disturbance localization algorithm |
| CN105488935B (en) * | 2015-12-25 | 2018-01-16 | 天津大学 | A kind of distributed optical fiber disturbance positioning system and its localization method based on asymmetric double Mach Zehnder interference |
| CN106441386B (en) * | 2016-09-29 | 2019-02-26 | 西南交通大学 | Data processing method and device based on distributed optical fiber sensing system |
| CN107270952B (en) * | 2017-07-27 | 2020-03-31 | 天津求实飞博科技有限公司 | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection |
-
2017
- 2017-07-27 CN CN201710624875.2A patent/CN107270952B/en active Active
-
2018
- 2018-04-26 WO PCT/CN2018/084568 patent/WO2019019735A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003029851A2 (en) * | 2001-09-28 | 2003-04-10 | University Of Southampton | Optical fibre-based devices utilising the raman effect |
| CN102589587A (en) * | 2012-02-13 | 2012-07-18 | 上海大学 | Improved short-term cross-correlation positioning method for chaos fiber fence system |
| CN104215271A (en) * | 2014-07-30 | 2014-12-17 | 复旦大学 | Positioning method for disturbance position in distributed optical fiber disturbance monitoring system |
| CN106872071A (en) * | 2016-12-30 | 2017-06-20 | 江苏骏龙光电科技股份有限公司 | A kind of temp measuring method based on optical frequency domain reflection technology |
Non-Patent Citations (1)
| Title |
|---|
| 40-km OFDR-Based Distributed Disturbance Optical Fiber Sensor;Tiegen Liu等;《IEEE PHOTONICS TECHNOLOGY LETTERS》;20160401;第28卷(第7期);第771页左栏第1段至第774页右栏第2段及图1-6 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN107270952A (en) | 2017-10-20 |
| WO2019019735A1 (en) | 2019-01-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107270952B (en) | Long-distance optical fiber distributed disturbance sensing signal processing method based on optical frequency domain reflection | |
| CN110579177B (en) | Optical frequency domain reflection distributed sensing demodulation method based on relative phase change | |
| CN103090961B (en) | Disturbance source positioning method of distributed type optical fiber sensing system | |
| CN103900623B (en) | Optical time domain reflectometer and its common mode inhibition method based on alliteration optical modulator | |
| CN107515033B (en) | Point type liquid level sensor device and its measurement method based on optical frequency domain reflection technology | |
| CN101625258B (en) | Optical fiber vibration sensing system based on Mach-Zehnder interferometer and sensing method | |
| US20200141769A1 (en) | Method for processing long-distance optical fiber distributed disturbance sensing signal based on optical frequency domain reflectometry | |
| CN103591971B (en) | A kind of localization method of fiber grating | |
| CN105466349B (en) | In a kind of probe beam deflation strain measurement sensitivity method is improved with thin cladded-fiber | |
| CN110487313A (en) | Light source frequency sweep Nonlinear Self-tuning method in optical frequency domain reflection technology | |
| CN204649162U (en) | A kind of fiber grating distributed strain pick-up unit | |
| CN103412137B (en) | With speed-measuring method and device in twiddle factor | |
| CN107782696B (en) | Sensing system and method for measuring refractive index of distributed liquid by using tapered optical fiber | |
| CN106452570A (en) | Optical fiber fault detection system and detection method based on optical fiber phase mediation principle | |
| CN107014409B (en) | A kind of long range optical frequency domain reflection-based optical fiber Distributed Multi destabilization sensing method | |
| CN104680696B (en) | A kind of fiber optic intrusion monitoring system | |
| CN107389154A (en) | The continuous liquid level sensing device of hollow optic fibre and measuring method based on OFDR | |
| Saxena et al. | Empirical mode decomposition based dynamic error correction in SS covered 62.5/125 µm optical fiber based distributed temperature sensor | |
| CN106017513A (en) | Measurement system based on optical coherent interference | |
| CN205607417U (en) | Disturbance signal measurement device of distributed optical fiber M -Z interferometer | |
| CN205593556U (en) | Novel high tension cable connects on -line monitoring device | |
| CN105716521A (en) | Device and method for enlarging measurement range of frequency domain low coherent light interference | |
| CN1664537A (en) | On-line modularized testing device for optical fiber ring in optic fiber gyroscope | |
| CN207515900U (en) | Optical fiber raster vibration measuring system based on pulse code and edge filter demodulation method | |
| CN113607074A (en) | Strain sensing demodulation method based on overlapping window in optical frequency domain reflection |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |