ASTM F3092-14(2024)

Standard Terminology Relating to Optical Fiber Sensing Systems

SIGNIFICANCE AND USE
3.1 Definitions in this standard are to be regarded as correct for the terms found in other ASTM standards of Committee F36. Certain terms may be found in more than one standard issued under the jurisdiction of this committee and many of these terms have been placed in this standard.
SCOPE
1.1 This terminology standard is a compilation of definitions of technical terms related to optical fiber sensing systems, used in the various sections of standards under the jurisdiction of ASTM Committee F36.  
1.2 Where possible, definitions are stated as a single sentence, with necessary supplementary information as a Discussion. This approach is used to simplify explanations of the meanings of technical terms for the benefit of those not conversant with them, to facilitate a precise understanding and interpretation of F36 ASTM standards.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2024
• ICS: 01.040.33 - Telecommunications. Audio and video engineering (Vocabularies)
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: F36 - Technology and Underground Utilities
• Drafting Committee: F36.91 - Terminology

Relations

• Replaces: ASTM F3092-14(2019) - Standard Terminology Relating to Optical Fiber Sensing Systems
• Effective Date: 01-Feb-2024

Overview

ASTM F3092-14(2024): Standard Terminology Relating to Optical Fiber Sensing Systems provides a comprehensive set of precise, standardized definitions for terms used in the field of optical fiber sensing. Developed by ASTM Committee F36, this international standard is designed to ensure clarity and uniformity in the language used across various ASTM standards, particularly those governing the technology and application of optical fiber systems. The terminology enhances communication, supports best practices, and simplifies complex technical concepts for both technical and non-technical stakeholders involved in optical fiber sensing projects.

Key Topics

This ASTM standard focuses on the following important topics, pivotal to optical fiber sensing systems and related underground utility applications:

• Comprehensive Definitions: The standard compiles clear, single-sentence definitions for technical terms with supplementary explanations, facilitating a better understanding of key concepts, such as absorption, attenuation, bandwidth, and coherence length.
• Consistency Across Documents: Terms defined in this standard are intended to be universally correct within all ASTM Committee F36 standards, promoting consistency across multiple documents and projects.
• SI Units Only: All values and measurements in the standard are stated in SI units to align with international best practices.
• Accessibility for Non-Experts: Definitions are worded to be accessible to those without an advanced technical background, supporting broader adoption and implementation.
• International Compliance: The terminology reflects principles established by the World Trade Organization’s Technical Barriers to Trade (TBT) Committee, supporting global standardization in optical fiber sensing.

Applications

The terminology defined in ASTM F3092-14(2024) is invaluable across a range of practical applications in industries using optical fiber sensing technology, such as:

• Infrastructure Monitoring: Supporting the deployment and maintenance of distributed optical fiber sensing systems for pipelines, sewers, and tunnels-improving safety, leak detection, structural health monitoring, and operational efficiency.
• Utility Management: Facilitating clear communication among engineers, operators, and contractors responsible for the installation, inspection, and ongoing management of optical fiber networks within underground utilities and distribution systems.
• System Design and Analysis: Providing a consistent language for discussing sensor calibration, spatial resolution, attenuation, and data interpretation-ensuring accurate system specification, operation, and troubleshooting.
• Training and Documentation: Serving as a reference for technical writing, training materials, and operational manuals, enabling teams to work from a shared vocabulary and minimizing misunderstandings.
• Regulatory Compliance: Assisting organizations in meeting international and national requirements by adhering to globally recognized terminology.

Related Standards

This standard is often used in conjunction with other ASTM standards and guidelines relevant to optical fiber sensing and underground utilities, including:

• ASTM F2233 – Guide for Safety, Access Rights, Construction, Liability, and Risk Management for Optical Fiber Networks in Existing Sewers
• ASTM F2303 – Practice for Selection of Gravity Sewers Suitable for Installation of Optical Fiber Cable and Conduits
• ASTM F2304 – Practice for Sealing of Sewers Using Chemical Grouting
• ASTM F2414 – Practice for Sealing Sewer Manholes Using Chemical Grouting
• ASTM F2454 – Practice for Sealing Lateral Connections and Lines from the Mainline Sewer Systems by the Lateral Packer Method, Using Chemical Grouting
• ASTM F2462 – Practice for Operation and Maintenance of Sewers with Optical Fiber Systems
• ASTM F2550 – Practice for Locating Leaks in Sewer Pipes By Measuring the Variation of Electric Current Flow Through the Pipe Wall

Referencing ASTM F3092-14(2024) in documents and contracts ensures the use of accurate, authoritative definitions, supporting quality assurance and interoperability in projects utilizing optical fiber sensing technologies.

Keywords: ASTM F3092, optical fiber sensing, fiber optic systems, terminology standard, distributed optical fiber sensing, underground utilities, fiber optic monitoring, standard definitions, infrastructure monitoring, ASTM Committee F36.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3092 − 14 (Reapproved 2024)
Standard Terminology
Relating to Optical Fiber Sensing Systems
This standard is issued under the fixed designation F3092; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope F2349 Practice for Operation and Maintenance of Integrated
Natural Gas Pipelines and Optical Fiber Systems (With-
1.1 This terminology standard is a compilation of defini-
drawn 2017)
tions of technical terms related to optical fiber sensing systems,
F2350 Practice for Selection of Natural Gas Pipelines Suit-
used in the various sections of standards under the jurisdiction
able for Installation of Optical Fiber Systems (Withdrawn
of ASTM Committee F36.
2017)
F2414 Practice for Sealing Sewer Manholes Using Chemical
1.2 Where possible, definitions are stated as a single
Grouting
sentence, with necessary supplementary information as a
F2454 Practice for Sealing Lateral Connections and lines
Discussion. This approach is used to simplify explanations of
from the mainline Sewer Systems by the Lateral Packer
the meanings of technical terms for the benefit of those not
Method, Using Chemical Grouting
conversant with them, to facilitate a precise understanding and
F2462 Practice for Operation and Maintenance of Sewers
interpretation of F36 ASTM standards.
with Optical Fiber Systems
F2550 Practice for Locating Leaks in Sewer Pipes By
1.3 The values stated in SI units are to be regarded as
Measuring the Variation of Electric Current Flow Through
standard. No other units of measurement are included in this
the Pipe Wall (Withdrawn 2022)
standard.
F2551 Practice for Installing a Protective Cementitious
1.4 This international standard was developed in accor-
Liner System in Sanitary Sewer Manholes
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the 3. Significance and Use
Development of International Standards, Guides and Recom-
3.1 Definitions in this standard are to be regarded as correct
mendations issued by the World Trade Organization Technical
for the terms found in other ASTM standards of Committee
Barriers to Trade (TBT) Committee.
F36. Certain terms may be found in more than one standard
issued under the jurisdiction of this committee and many of
2. Referenced Documents
these terms have been placed in this standard.
2.1 ASTM Standards:
4. Terminology
F2233 Guide for Safety, Access Rights, Construction,
4.1 Terms and Definitions:
Liability, and Risk Management for Optical Fiber Net-
absorption, n—the loss of some or all of the energy contained
works in Existing Sewers
in an electromagnetic wave to the medium in which it is
F2303 Practice for Selection of Gravity Sewers Suitable for
propagating, usually converted to heat.
Installation of Optical Fiber Cable and Conduits
F2304 Practice for Sealing of Sewers Using Chemical acceptance angle, n—the maximum angle, measured from the
optical fiber centerline to an incident light ray, within which
Grouting
the incident ray will be accepted for transmission by total
internal reflection along the fiber.
DISCUSSION—If the incident angle is greater than the acceptance
This terminology is under the jurisdiction of ASTM Committee F36 on
angle, total internal reflection will not occur and the incident ray will be
Technology and Underground Utilities and is the direct responsibility of Subcom-
lost by leakage.
mittee F36.91 on Terminology.
Current edition approved Feb. 1, 2024. Published February 2024. Originally
access rights, n—agreements between various parties to obtain
approved in 2014. Last previous edition approved in 2019 as F3092 – 14 (2019).
temporary and permanent access to property for the purpose
DOI: 10.1520/F3092-14R24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3092 − 14 (2024)
of constructing, maintaining, or changing optical fiber authorized inspector, n—the person(s) contracted or approved
networks. F2233 by the owner or owner’s representative to do inspections.
F2414
accuracy, n—the closeness of the measured value to the true or
the ideal value of the parameter being measured and is
backfill, n—in tunneling, a material used to replace excavated
affected by both bias and precision. soil.
acoustic wave, n—longitudinal waves propagated by means of
bandwidth, n—the range of frequencies that a device is
adiabatic compression and decompression.
capable of handling.
acousto-optics, n—the science and technology of the interac-
beam splitter, n—an optical device for dividing a light beam
tions between sound waves and light waves passing through
into two separated beams.
material media, especially as applied to the modulation and
bench, n—in tunneling, in situ ground at the lower face of a
deflection of laser beams by ultrasonic waves.
tunnel undergoing staged excavation.
acrylamide, n—organic solid of white, odorless, acrylic resin-
bend loss, n—optical power loss in an optical fiber because
ous material available in flake-like crystals and in liquid
signal radiation escapes through its bends, with the magni-
form. The greatest use of acrylamide is as a coagulant aid in
tude of optical power loss being proportional to the bending
drinking water treatment. Other major uses of acrylamide are
radius.
in soil stabilization, in grout for repairing sewers, and in
acrylamide gels used in biotechnology laboratories. F2414
bending radius, n—the radius of a bend measured in a fiber
optic cable.
acrylate, n—a general term applied to various water-soluble
acrylic resinous materials. F2414
bentonite, n—clay composed mainly of clay mineral
‘montmorillonite,’ used for synthetic reasons, due to its
adit, n—in tunneling, a tunnel driven from ground surface to
expanding properties when in contact with water, for
provide access to or drainage from underground workings; a
example, drilling mud, binder, absorbent, groundwater
length of tunnel driven for an exploration-exploration adit.
barrier, etc.
advance, n—in tunneling, the forward progress in the construc-
bias, n—the difference between the measured results after
tion of a tunnel, usually measured by the length created, or
averaging, less the true value.
the rate of segment positioning in terms of a number per
hour/day or some other timescale.
birefringence, n—the separation of a light beam into two
components to form two rays propagating at different
ambient temperature, n—the temperature of the surrounding
velocities in the medium.
environment or air. F2304
-1 -1
bolt pocket, n—in tunneling, a pre-formed recess in tunnel
Angstrom, A, n—a unit of length equal to 10 nanometer (10
-4 -6 -10 -10
segment to accommodate bolts which hold segments to-
nm), 10 micron (10 mm), and 10 meter (10 m).
gether.
annulus, n—in tunneling, a ring-shaped opening, generally
bore, n—in tunneling, the internal diameter of a pipe or other
bounded by the outside diameter of excavated tunnel and the
exterior of the final tunnel liner. F2304 cylinder, single tunnel, for example, twin bore.
aperture, n—in optics, a hole or an opening through which borehole, n—a hole driven into the ground to get information
light travels. about the strata, or to release water pressure by vertical sand
drains, or to obtain water, oil, gas, etc.
attenuation, n—the decrease in optical power of a signal, or
light wave, from interaction with the propagation medium,
boring/bored, n—making a hole in the ground by means of
for example, absorption, reflection, diffusion, scattering, rotating auger.
deflection, dispersion or resistance.
box jack/jacked box, n—in tunneling, a fully constructed
attenuation budget, n—the maximum cumulative one-way or structure that is thrust into final position from an adjacent
two-way optical power loss between the interrogator and the
jacking point.
measurement point that allows a measurement with a speci-
Bragg cell, n—an acousto-optic device that is capable of
fied performance.
modulating light waves to produce an output light wave with
attenuation range, n—total cumulated optical loss (one way
an imposed frequency equal to the frequency of the input
loss; expressed in decibels (dB)) tolerated by the DRS
signal.
system without affecting the specified measurement perfor-
Brillouin optical time domain analysis, BOTDA, n—double
mance more than a given factor at a given location, spatial
ended access to the light source and detection system for
resolution, and measurement time.
long sensing lengths combined with high strain and tempera-
DISCUSSION—Part of the total cumulative loss can be the fiber
ture resolution for up to 31 miles (50 km) without signal
attenuation, point defect losses introduced by components such as
connectors, splices, kink in the fiber, attenuators, etc. regeneration.
F3092 − 14 (2024)
Brillouin optical time domain reflectometer, BOTDR, n—a cladding, n—in optics, optical transparent material over the
single ended access to the source and detection system, core of the optical fiber, with a refractive index lower than
which provides a Brillouin gain-loss-based distribution sen- that of the core, to provide total internal reflectance.
sor much like the standard OTDR sensors which use
coherence length, n—the coherence time of a light beam
Rayleigh scattering to the same effect. See optical time
multiplied by the velocity of the light.
domain reflectometer.
coherence time, n—if t is the time a light beam takes to
Brillouin scattering, n—light in a medium interacts with
become coherent, and t + Δt is the time at which the light
time-dependent optical density variations and changes its
beam loses its coherent properties, Δt is the coherence time.
frequency and path.
DISCUSSION—The density variations may be due to acoustic modes,
coherent light, n—light which has predictable parameters at
such as phonons, or magnetic modes, such as temperature gradients. As
any point in time or space, for example, laser light.
described in classical physics, when the medium is compressed its
index of refraction changes, and a fraction of the traveling light wave,
combined sewers, n—sewers that carry both wastewater and
interacting with the periodic refraction index variations, is deflected as
storm or surface water. F2303
in a three-dimensional diffraction grating. Since the sound wave, too, is
traveling, light is also subjected to a Doppler shift, so its frequency
compensation grouting, n—in tunneling, a method of revers-
changes.
ing ground settlements by injecting grout into the ground.
cable, n—a group of insulated light conductors that are bound
competent person, n—a person properly trained in the safety
together, usually with a durable cable jacket.
aspects of an activity. F2233
cable jacket, n—the outer protective covering over insulated
conductor, n—a transparent medium that is capable of trans-
conductors that are bound together.
mitting or conveying light waves by total internal reflection.
caisson, n—in tunneling, a watertight retaining structure, that
conduit, n—plastic tubing used to house optical fiber cable that
can be used as a support of excavation for a shaft structure.
is connected to, but not inside of, a pipeline. F2349, F2462
canopy tube, n—in tunneling, a metal tube drilled into the
confined space, n—an enclosed area that is large enough and
tunnel face above the ground to be excavated, the tube is
so configured that a person can bodily enter and has the
pumped full of grout once in place; the canopy is created
following characteristics: its primary function is something
using multiple adjacent tubes to reduce the risk of crown
other than human occupancy; has restricted entry and exit.
failure.
(Restricted entry and exit is a physical configuration which
catalyst, n—substance which markedly speeds up the cure of
requires the use of hands or contortion of the body to enter
an adhesive when added in small quantities as compared to into or exit from the confined space.) F2233
the amounts of primary reactants. F2414
connector, n—coupling device attached to the end of a fiber so
caulking, n—one of several different processes to seal joints or that it can be mechanically connected to equipment or mated
seams in various structures and piping. F2454
with another connector to join two fibers together by
aligning their cores to minimize signal loss.
character-separated value file format, CSV, n—synonymous
with “comma separated value file,” stores tabular data
connector insertion loss, n—the power loss due to the
(numbers and text) in a sequence of characters, with no data
insertion of a connector between two elements.
that has to be interpreted, separated by some character or
constructability, n—the term used to denote the condition of a
string, for example, comma or tab.
completed set of plans and specifications for an optical fiber
characteristic frequency and/or wavelength at reference
network and its impact to the host utility, which have been
temperature (Brillouin technologies), n—the frequency
prepared with an analysis of practical, feasible methods of
and/or wavelength that characterizes the sensor response at
construction. F2233
reference temperature as monitored by the interrogator.
contractor, n—usually, the entity in charge of construction of
DISCUSSION—As Brillouin frequency varies with wavelength of the
the new tunnel or other infrastructure that may impact the
light source, this also changes the temperature and strain coefficients
for various sensing fibers. Therefore, characteristic frequency and the utility. F2551
wavelength at a specified reference temperature and at zero strain are
control agent, n—substance added which controls the viscos-
usually provided by the complete system producers.
ity or flow properties of the material it is added to. F2414
chemical grout, n—injection repair media other than cemen-
titious grout that may be multicomponent, with or without convergence, n—in tunneling, a measurement of the inward
additives, and based on either polyurethane resin or acrylic movements of tunnel walls, often monitored to provide
resin. F2414 information on the performance of the lining during con-
struction.
circumferential joint, n—in tunneling, a joint (typically be-
tween segments) which runs circumferentially relative to the conveyor, n—in tunneling, used to remove excavated material
tunnel bore. from a tunnel face or shaft.
F3092 − 14 (2024)
core, n—the primary light-conducting region of an optical cut and cover tunnel, n—in tunneling, a method of tunnel
fiber. The refractive index of the core is higher than its construction involving excavating a trench, installing the
cladding, the condition necessary for total internal reflection. structure and covering it over, generally used for shallow
tunnels.
coupler, n—a mechanical connector that is used to interconnect
two or more optical fibers. data link, n—a communication link suitable for transmission
of data, which does not include the data source and the data
coupler 3-dB, n—a coupler that splits the optical energy in an
sink.
optical waveguide into two equal parts and couples each part
into a separate waveguide; ideally distributes 50 % of the
decibel, dB, n—a gain or attenuation factor, measured as 10
input optical power to each of the output channels. times the log of a power ratio.
coupling, n—the connection between elements, whether physi-
delay distortion, n—in a waveform or signal that contains two
cal or across a gap, where energy from one element is
or more different frequencies, that is, different wavelengths,
transferred to one or more other elements.
such as that occurs in the spectral width of an optical pulse,
distortion caused by the difference in arrival times of the
coupling loss, n—the power loss caused by the coupling.
frequencies at the output of a transmission system, for
example, as at the end of a fiber optic link.
coupling ratio, n—the ratio of the output power to the input
power.
demodulation, n—the extraction of the original signal from
the carrier.
covered tasks, n—an activity, identified by the operator, that is
performed on a pipeline; is an operations and maintenance
designated control point, DCP, n—specific documented loca-
task; is performed as a requirement of this part and affects
tions in the pipeline system where the operations plan
operation or integrity of the pipeline. F2349
designates the control of gas. F2349
critical angle, n—measured angle between the incident ray and
detector, n—a device that responds to a signal and reproduces
the normal to the reflecting surface where total internal
the signal in a new form, usually in a form that is easier to
reflection begins.
process.
DISCUSSION—Total internal reflection continues for all angles greater
than the critical angle.
dewatering, n—the removal of water from soils, normally
carried out with well points alone, or in combination with an
critical radius, n—the radius of curvature of an optical fiber
impermeable cut-off wall.
containing an axially propagated light wave at which mi-
crobend losses begin to occur.
diaphragm wall, n—a concrete retaining wall (usually rein-
forced) constructed by installing adjacent panels of concrete
cross passage, n—in tunneling, a small tunnel used to connect
underground, using the following method: excavate panel
between adjacent tunnel bores in a multiple-bore tunnel.
opening under pressure from drilling mud; lower reinforce-
cross-sensitivity, n—the unwanted change of measured result
ment cage into place (if applicable); pour concrete into the
due to the influence of physical factors other than the
hole, displacing the drilling mud.
measured parameters.
diffraction, n—the bending of radio, sound, or light waves
crown, n—in tunneling, the highest point of the internal curved
around an edge; typically aperture edges.
surface of a tunnel cross section.
diffuse reflectance spectroscopy, DRS, n—non-invasive tech-
culvert, n—small channel or drain used to carry water beneath
nique that measures the characteristic reflectance spectrum
an obstacle.
produced as light passes through a medium, by measuring
absorption and scattering.
cured-in-place pipe, CIPP, n—a trenchless rehabilitation
method used to repair existing pipelines.
discharge hose, n—a flexible tubing that facilitates outflow
DISCUSSION—The cured in place lining process consists of a flexible
through which the hot water or steam condensate is released
resin-saturated felt tube made of polyester or another resin, fiberglass
after flowing through the CIPP liner that is being cured.
cloth or a number of other materials suitable for resin impregnation,
which is inverted or pulled into a damaged pipe. Little to no digging is
discrete thermal elements, n—temperature monitoring com-
involved in this trenchless process, which potentially allows this
ponents that are not continuous.
method to be more cost-effective and less disruptive than traditional
“dig and replace” pipe repair methods. Once flexible resin impregnated
dispersion, n—in optics, wavelength dependent time-of-flight
lining is installed in damaged pipe, hot water, UV light, ambient cured
of an optical signal resulting from the fact that the index of
or steam is used to cure the resin and form a tight-fitting, jointless and
refraction of a fiber is wavelength dependent, that is, if the
corrosion-resistant replacement pipe.
refractive index, n, of a medium on the wavelength, l, then
cutterhead, n—in tunneling, the head at the front of a tunnel
dispersion = dn/dl.
boring machine used for cutting into the ground.
distance measurement range, n—maximum distance (speci-
DISCUSSION—The cutterhead is designed for specific soil types, for
example, hard rock, soft ground, high pressure, etc. fied in length units) from the DTS output connector along the
F3092 − 14 (2024)
DISCUSSION—Electrostrictive pressure is the result of electrostriction,
fiber optic sensor within which the instrument measures a
an acoustic wave created by the propagation of the two light waves,
temperature with specified measurement performance under
specifically the Stokes (probe) wave and the pump wave.
defined conditions.
DISCUSSION—This supporting parameter is closely related to the
electro-optic device, n—a device that converts electronic
attenuation range of the instrument. In test cases used to prove or verify
signals to optic signals or optic signals to electronic signals.
the reported specifications, the total fiber length shall be equal to or
greater than the specified distance measurement range (equal to or
emergency incident, n—an emergency incident may involve
greater than twice the distance measurement range in the loop configu-
fire, damage to underground facilities, explosion, gas leak,
ration).
injury, death, gas outage, district pressure problems, hazard-
ous or toxic material spills, or response by fire, police, or
distortion, n—in electronics, to reproduce or amplify (a signal)
other agencies. F2349
inaccurately by changing the frequencies or unequally
changing the delay or the amplitude of the components of the
engineer, n—the licensed professional engineer registered in
output wave.
the state where the work is being done designated by the
owner/operator of the utility or the tunnel, to represent the
distributed acoustic sensing, DAS, n—a system using fiber
owner’s/operator’s interests during the ground movement
optic cables to provide distributed strain sensing over its
monitoring process or pipe renovation process. F2303
entire length.
environmental temperature repeatability, n—difference of
distributed optical fiber sensing system, DOFSS, n—a sys-
the measured constant fiber optic sensor temperature at a
tem using optical fiber cable as a sensor, without discrete
specified instrument temperature (for example, nominal
elements such as wound mandrels or fiber Bragg gratings,
operating temperature) before and after temperature cycling
that is sensitive over its entire length to deliver spatially
of the instrument across the entire instrument operating
continuous and resolvable data on the desired measured
temperature range.
parameters.
environmental temperature stability, n—difference of the
distributed temperature gradient sensing, DTGS, n—a sys-
measured constant fiber optic sensor temperature before,
tem using optical fiber cable to measure temperature tempo-
during and after temperature cycling of the DTS instrument
ral and spatial gradients using thermal strain and thermo-
across the entire instrument operating temperature range.
optic effects.
DISCUSSION—Worst case environmental temperature effect, high/low
distributed temperature sensing, DTS, n—devices which
environmental temperature effect, and environmental temperature re-
measure temperatures by means of optical fibers function as peatability are derived from this definition.
liner sensors, temperatures are measured along the optical
evanescent wave, n—the wave radiating away from the fiber at
sensor cable to provide a continuous profile.
sharp bends in the optical fiber where the radius of the bend
is less than the critical bending radius.
distribution lines, n—a pipeline other than a gathering or
transmission line. F2349
exfiltration, n—leaking or weeping to the external areas
outside the barrier from a source inside the barrier. F2414
drift, n—a slow change in time of the monitoring characteris-
tics of the measurement system.
expanded gasket procedure, EGP, n—the sealing of joints,
cracks, or holes by soaking dry, oil-free oakum with chemi-
drill and blast, n—in tunneling, the excavation of a tunnel,
cal grout and forcing the oakum/resin plug into the opening
shaft, or cavern in rock using explosive charges place in
until it sets. F2414
holes drill in the face.
expanded lining, n—in tunneling, primary lining that consists
durability, n—a quality of a manufactured component of a
of segments that are expanded circumferentially against the
measurement system or of the entire measurement system
surrounding ground.
measured by how well it withstands a sustained period of
specified operation.
extrados, n—the outside face of a structure element.
earth pressure balance machine, EPBM, n—in tunneling, a
eye, n—in tunneling, the start of a tunnel, normally at a
type of tunnel boring machine which retains a prescribed
junction between a shaft and a tunnel.
amount of excavated soil in the cutterhead, in an effort to
equal the pressure in front of the machine, this method
Fabry Perot interferometer, n—a high resolution multiple
reduces the risk of soil running into the machine causing beam interferometer especially sensitive to linear motion of
excessive settlements above.
the mirrors.
electromagnetic interference, EMI, n—the interference face dowel, n—in tunneling, a rod of steel or fiberglass inserted
caused in a circuit by radiation through coupling.
into the tunnel face to provide temporary support and assist
in limiting face movement.
electrostriction, n—in optics, physical mechanism that ac-
counts for a material density change induced by an electric face loss, n—in tunneling, the loss of material from the face of
field in an isotropic body. a tunnel.
F3092 − 14 (2024)
failure criteria of the sensor, n—the measurement uncertainty greenfield settlement, n—vertical downward movement of the
due to overstressing, overheating, and other factors leading ground solely due to the loss of soil caused by tunneling.
to results or data that are unreliable.
groundwater, n—water beneath the surface of the ground.
fault, n—in geology, a crack in the earth’s crust resulting from
grout, n—in soil and rock grouting, a material injected into a
the displacement of one side with respect to the other on the
soil or rock formation to change the physical characteristics
scale of observation.
of the formation, usually made of sand, water, and cement.
fiber, n—optical: any type of optical fiber.
grout, n—in tunneling, a construction material used to improve
fiber loss, n—power loss in an optical fiber, usually expressed
ground conditions, fill voids in the ground or embed rein-
in dB/km.
forcing bars, as well as fill the annulus between the exca-
vated tunnel and the exterior of the final tunnel liner, usually
fiber optic, n—pertaining to optical fiber systems, such as
made of sand, water, and cement.
sensors and communication systems.
heat differential, n—measurement of small temperature dif-
fiber optic array, n—device that connects optical fibers to
ferences reliably performed by detecting the phase difference
optical waveguide devices which are necessary for wave-
with the interference light and using a thermally symmetric
length division multiplexing applications.
configuration.
fiber optic cable, n—optical fibers incorporated into a cable.
heterodyne detection, n—signal detection based on the mix-
fiber optic data link, n—a data link consisting of a modulated
ing of two frequencies.
light source, a fiber optic cable, and a photo-detector.
heterodyning, n—the mixing of an electromagnetic wave of
fiber optic sensor, n—a sensor in which light is modulated by
one frequency with a wave of another frequency to produce
a specified environmental variable.
a beat, usually for demodulation.
fiber optic sensor cable, n—cable formed using one or more
high/low environmental temperature effect, n—difference of
strands of optical fiber to sense physical or other parameters
the measured constant fiber optic sensor temperature at the
of interest and/or transmit data.
high and low temperature limit of the instrument tempera-
ture operating range.
fiber optic sheath, n—an outer protective covering over an
optical fiber, or a cable.
high-pressure distribution system, n—a distribution system
in which the gas pressure in the main is higher than the
fiber optic splice, n—a non-separable junction, usually formed
pressure normally provided to the customer (that is, higher
by fusing the end of one optical to another.
than utilization pressure). F2350
fiber optics, FO, n—the theories and practices of using the
homodyne detection, n—signal detection based on the use of
technologies for control and guidance of optical power.
only one frequency.
fiber to the x, FTTX, n—a generic term for any broadband
homogeneous curing, n—equal curing rate in all directions
network architecture using optic fiber to provide all or part of
and positions of a material.
the local loop used for last mile communications.
host pipe, n—in reference to CIPP, the original damaged pipe
frequency-division multiplexing, FDM, n—multiplexing in
containing the installed CIPP liner.
which the transmission frequency range is divided into
narrow bands, each used as a separate channel.
hot spot, n—length of fiber optic sensor (ΔL) which is exposed
by a measurable temperature change ΔT which is signifi-
fusion splicing, v—is the process of fusing or welding together
cantly bigger than the instrument temperature repeatability
two fibers, usually by an electric arc.
and which is confirmed by reference temperature devices in
gas, n—utilities, natural gas. F2350
the two thermal chambers.
gauge length, GL, n—is the length of the measured structure
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