Types of fiber optic patch cord interface and the scope of application
Fiber optic patch cords are classified and outlined as follows:
Fiber optic patch cords (also known as fiber optic connectors), that is, access to the optical module of the optical fiber connector, there are many kinds of, and can not be interoperable with each other. sFP module connected to LC fiber optic connector, and the gbcic connected to the SC fiber optic SFP module to LC fiber connector, and GBIC to SC fiber connector. The following is a detailed description of the network engineering of several commonly used fiber optic connectors:
①FC-type fiber optic patch cord: the external reinforcement is the use of metal bushings, fastening for the screw buckle. Generally used in the ODF side (the most used on the distribution frame)
② SC-type fiber optic patch cord: connect the GBIC optical module connector, its shell is rectangular, the fastening method is the use of plug pin latch type, do not need to rotate. (Routers and switches on the most)
③ST-type fiber optic patch cord: commonly used in fiber optic distribution frames, the shell is round, the fastening method for the screw buckle. (For 10Base-F connection, the connector is usually ST type. Commonly used in fiber optic distribution frames)
4 LC type fiber optic patch cord: connectors for SFP modules, which are made with easy-to-operate modular jack (RJ) latch mechanism. (Router commonly used)
⑤MT-RJ type fiber optic patch cord: transceiver integrated square fiber optic connector, one end of the dual-fiber transceiver integrated
ST, SC connector connector connector is commonly used in the general network. ST head inserted into the rotating half a week there is a bayonet fixed, the disadvantage is that it is easy to break; SC connector head directly inserted and extracted, the use of a very easy to use, the disadvantage of easy to fall out of the FC connector head is generally used in telecom networks, there is a screw cap. Telecom network, there is a screw cap screwed to the adapter, the advantage is reliable, dust-proof, the disadvantage is that the installation time is a little long.MTRJ-type fiber optic patch cord consists of two high-precision plastic molding connector and fiber optic cable components. The outer parts of the connectors are precision plastic parts, including push-pull type insertion and removal clamping mechanism. Suitable for indoor applications in telecom and data network systems.
Fiber Optic Module: generally support hot-swappable, GBIC using fiber optic interfaces are mostly SC or ST type; SFP, that is: small package GBIC, the use of optical fiber for LC type.
The use of fiber:
Single-mode: L wavelength 1310 single-mode long-haul LH wavelength 1310,1550
Multi-mode: SM wavelength 850
SX/LH that can be used with single-mode or multi-mode fibers
In the indication of the pigtail connector marked, we often see the "FC/PC", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", "SFP", and so on. PC", "SC/PC" and so on, its meaning is as follows
1"/" in front of the part of the connector indicates that the pigtail fiber connector type
"SC "The connector is a standard square connector, the use of engineering plastics, with high temperature resistance, not easily oxidized advantages. SC connectors are generally used for optical interfaces on the side of transmission equipment
"LC" connectors are similar in shape to SC connectors and are smaller than SC connectors.
"FC" connector is a metal connector, generally used in the ODF side, the metal connector can be plugged and unplugged more often than plastic.
Connector varieties signal more, in addition to the three introduced above, there are MTRJ, ST, MU, etc.
2. '/' after the indication of fiber optic connector cross-section process, that is, the grinding method
"PC" in the telecom operator's equipment is the most widely used, and its connector The cross section is flat.
"UPC" attenuation is smaller than "PC", generally used for special needs of the equipment, some foreign manufacturers ODF frame internal jumpers are FC/UPC, mainly to improve the ODF device's own indicators.
In addition, in the broadcasting and early CATV in the application of more "APC" model, the pigtail head with a tilted end, can improve the quality of the TV signal, the main reason is that the TV signal is an analog optical modulation, when the joint coupling surface is vertical, the reflected light along the original path back.
Because of the uneven distribution of the refractive index of the fiber will return to the coupling surface, although the energy is very small, but because the analog signal is unable to completely eliminate the noise, so it is equivalent to the original clear signal superimposed on the signal with a time delay of the weak signal, the performance of the screen is a double image. Pigtail head with tilt can make the reflected light does not return along the original path. General digital signals generally do not have this problem.
Usage range:
A: Fiber optic communication system
B: Fiber optic broadband access network
C: Fiber optic CATV
D: LAN
E: Fiber optic instrumentation meter
F: Fiber optic sensor
G: Fiber optic teach-in system
H: Testing
The classification of optical fiber is mainly from the working wavelength, refractive index distribution, transmission mode, raw materials and manufacturing methods
to make a summary of the various classifications are listed below.
(1) working wavelength: ultraviolet fiber, visible fiber, near infrared fiber, infrared fiber (0.85pm, 1.3pm,
1.55pm).
(2) Refractive index distribution: step (SI) type, near-step, gradient (GI) type, others (e.g., triangular, W-type,
concave, etc.).
(3) Transmission modes: single-mode fiber (including polarization-holding fiber, non-polarization-holding fiber), multi-mode fiber.
(4) raw materials: quartz glass, multi-component glass, plastics, composite materials (such as plastic cladding, liquid fiber core, etc.),
infrared materials and so on. According to the coated material can also be divided into inorganic materials (carbon, etc.), metal materials (copper, nickel, etc.) and plastic
etc.
(5) Manufacturing methods: Pre-plasticization with vapor-phase axial deposition (VAD), chemical vapor deposition (CVD), etc., drawing method has
Tube law (Rod intube) and double crucible method, etc..
Two, quartz optical fiber
is silica (SiO2) as the main raw material, and according to different doping, to control the core and cladding
refractive index distribution of the optical fiber. Quartz (glass) series of optical fibers, with low consumption, broadband characteristics, is now widely
used in cable television and communications systems.
Fluorine Doped Fiber (Fluorine Doped Fiber) is one of the typical products of quartz fiber. Usually, as
1.3Pm wave domain communication fiber, control the core of the dopant for the dioxide (GeO2), cladding is made of SiO
fried. However, the core of the fluorine-connected fiber, most of the use of SiO2, but in the cladding is doped with fluorine. Because,
Rayleigh scattering loss is a phenomenon of light scattering caused by the change of refractive index. Therefore, it is desirable to have fewer dopants to contribute to the refractive index variation
factor.
Fluorine is mainly used to reduce the refractive index of SIO2. Thus, it is commonly used for doping of the cladding. Since
Fluorine doped fiber, the core does not contain fluorine dopants that affect the refractive index. Because of its Rayleigh scattering is very small, and
loss is close to the theoretical minimum. So it is mostly used for long distance optical signal transmission.
Quartz fiber (Silica Fiber) and other raw materials compared to the optical fiber, but also from the ultraviolet light to the near-red
Outer light transmission of a wide range of spectral, in addition to communications purposes, but also can be used in the field of light guide and conductive images.
Third, infrared optical fiber
The operating wavelength of the quartz optical fiber developed in the field of optical communication is only 2 pm, even though it is used for shorter transmission distances.
To this end, the optical fiber developed in the field of longer infrared wavelengths is called an infrared optical fiber.
Infrared optical fiber (Infrared Optical Fiber) is mainly used for light energy transmission. Examples include: temperature measurement,
thermal image transmission, laser scalpel medical treatment, thermal processing, etc. The penetration rate is still low.
Four, compound optical fiber
Compound fiber (Compound Fiber) in the SiO2 raw materials, and then mixed appropriately, such as sodium oxide (Na2O),
Boron oxide (B2O2), potassium oxide (K2O2), and other oxides of the composition of glass made of optical fiber, featuring a multi-composition
Component of glass than the softening point of quartz, and the core and cladding. Lower and the core and cladding refractive index difference is very large. Mainly used in the medical business of fiber optic
endoscopes.
V, Fluoride Fiber
Chloride fiber (Fluoride Fiber) is made of fluoride glass optical fiber. This fiber material and
abbreviation ZBLAN (that is, aluminum fluoride (ZrF4), barium cyanide (BaF2), lanthanum fluoride (LaF3), aluminum fluoride
(A1F2), sodium cyanide (NaF) and other chlorinated glass raw materials into a simplified acronym. Mainly work in 2 ~ 10pm
wavelength optical transmission business.
Because ZBLAN has the possibility of ultra-low-loss optical fiber, is being used for long-distance communication optical fiber can be
Practical development, for example: its theoretical minimum loss, in the 3pm wavelength up to 10-2 ~ 10-3dB / km, while
quartz fiber at 1.55pm but in the 0.15 ～to 0.16dB/Km.
At present, ZBLAN fiber can only be used for temperature sensors and thermal
image transmission at 2.4 to 2.7 pm due to the difficulty in reducing scattering loss, and has not been widely used.
Recently, a 1.3pm fault-doped fiber amplifier (PD
FA) is being developed for long-distance transmission using ZBLAN.
Six, Plastic Clad Fiber
Plastic Clad Fiber (Plastic Clad Fiber) is a high-purity quartz glass as the core, and the refractive index is slightly lower than the quartz, such as silicone and other plastics as a cladding step-type optical fiber. Compared with quartz fiber, it has
core rent, high numerical aperture (NA). Therefore, it is easy to combine with light-emitting diode LED light source, and the loss is
smaller. Therefore, it is very suitable for local area networks (LAN) and close-range communications.
VII, plastic optical fiber
This is the core and cladding are made of plastic (polymer) optical fiber. Early products are mainly used for decorative and
Guided lighting and optical communication in the short-distance optical keyway.
The raw materials are mainly plexiglass (PMMA), polystyrene (PS) and polycarbonate (PC). Losses are constrained by the inherent C-H bonding structure of the
plastic, generally up to tens of dB per kilometer, in order to reduce losses are being developed and applied
Fluorosol series of plastics. As plastic optical fiber (Plastic Optical fiber) core diameter of 1000pm,
100 times larger than single-mode quartz fiber, simple splicing, and easy to bend construction is easy. In recent years, coupled with the progress of broadbandization
the development of multi-mode plastic optical fiber as a gradual-index (GI) refractive index has attracted the attention of the society. Recently,
it has been rapidly used in LAN inside automobiles, and may be used in home LAN in the future.
VIII, single-mode fiber
This refers to the working wavelength, can only transmit a propagation mode of optical fiber, usually referred to as single-mode fiber
(SMF: Single ModeFiber). Currently, it is the most widely used fiber in cable television and optical communications.
Because the core of an optical fiber is very thin (about 10 pm) and the refractive index is distributed in a step-like manner, when the normalized frequency V parameter
number <2.4, theoretically, can only form a single-mode transmission. In addition, SMF has no multimode dispersion, not only the transmission bandwidth
is wider than that of multimode fibers, but also the material dispersion and structural dispersion of SMF are summed up and offset, and its synthetic characteristics are exactly shaped
into a zero-dispersion characteristic, which makes the transmission bandwidth even wider.
There are many types of SMFs, depending on the dopant and manufacturing method. DePr-
essed Clad Fiber (DePr-
essed Clad Fiber), whose cladding forms a two-fold structure, adjacent to the core of the cladding, the refractive index is lower than that of the outer inverted cladding
. In addition, there are matched cladding fibers with a uniformly distributed cladding refractive index.
Nine, multi-mode fiber
The optical fiber according to the work of the length of its propagation of the possible modes for a number of modes of the optical fiber is called multi-mode fiber (MMF:
MUlti ModeFiber). The core diameter is 50 pm, and since the transmission modes can be up to several hundred, the transmission
bandwidth is mainly governed by mode dispersion compared to SMF. Historically, it has been used for short-distance transmission in cable television and communications systems. Since
From the emergence of SMF fiber, it seems to form a historical product. However, in reality, MMF is more advantageous in many LANs due to its larger core diameter than SMF and the ease of combining it with light sources such as LED
. Therefore, MMFs are still gaining renewed
attention in the field of short-range communication.
When MMFs are categorized according to the refractive index distribution, there are two types: gradient (GI) type and step (SI) type.
The refractive index of the GI type
is the highest in the center of the core, and then decreases slowly along the cladding. From a geometric optics point of view, the light beam advancing in the core
appears to travel in a serpentine fashion. Since, each path of light takes approximately the same amount of time. Therefore, the transmission
capacity is larger than that of SI type.
The refractive index distribution of SI-type MMF fiber, the core refractive index distribution is the same, but the interface with the cladding is
stepped. Due to the SI-type light wave reflection in the fiber forward process, resulting in the time difference between the various optical paths, resulting in
ejection of light wave distortion, color excitation is larger. As a result, the transmission bandwidth becomes narrower, and SI-type MMFs are less used at present.
Ten, dispersion-shifted fiber
Single-mode fiber operating wavelength at 1.3Pm, the mode field diameter of about 9Pm, the transmission loss of about 0.3dB/km.
Then, the zero-dispersion wavelength is exactly at 1.3pm.
In quartz fiber, the 1.55pm section has the smallest transmission loss (about 0.2dB/km) from the raw material. Since
now has practical erbium-doped fiber amplifier (EDFA) is working in the 1.55pm band, if in this band also
can achieve zero dispersion, it is more conducive to the application of 1.55Pm band of long-distance transmission.
So, by cleverly using the quartz material dispersion in the optical fiber material and the core structure dispersion of the synthetic offset characteristics,
it can make the original zero dispersion in the 1.3Pm band, shifted to the 1.55pm band also constitutes zero dispersion. Therefore, it is named Dispersion Shifted Fiber (DSF: DispersionShifted Fiber).
The method of increasing the structural dispersion is mainly to improve the refractive index distribution properties in the fiber core.
In the long-distance transmission of optical communications, the fiber dispersion of zero is important, but not the only. Other properties
There are low loss, easy splicing, cable formation, or little change in operating characteristics (including bending, stretching, and the effects of environmental changes
The DSF is designed with a combination of these factors in mind.
XI Dispersion Flat Fiber
Dispersion Shifted Fiber (DSF) is the design of a single-mode fiber with zero dispersion located in the 1.55pm band.
Dispersion Flattened Fiber (DFF: Dispersion Flattened Fiber) is the dispersion from 1.3Pm to 1.55pm of the wider band of dispersion, can be made very low, almost zero dispersion of the optical fiber is called DFF. because the DFF to be made to
1.3pm ~ 1.55pm range of dispersion are reduced. The dispersion is reduced in the range of 1.3pm to 1.55pm. It requires a complex design of the refractive index distribution of the fiber.
However, this type of fiber is suitable for wavelength division multiplexing (WDM) lines. Because the process for DFF fiber is more
complex, it is more expensive. Prices will decrease in the future as production volumes increase.
Twelve dispersion-compensated fibers
For the trunk system using single-mode fibers, since most of the use of 1.3pm band dispersion of zero optical fiber
constructed. However, nowadays, 1.55pm, which is the smallest loss, is being made practical by EDFA, and it would be beneficial if 1.55pm wavelengths could be operated on 1.3pm zero-dispersion fibers as well.
Because of this, the 1.3pm wavelength can be operated at the same time.
Because, in a 1.3Pm zero-dispersion fiber, the dispersion in the 1.55Pm band is as much as about 16ps/km/nm.
If in this fiber optic line, insert a section of fiber with the opposite sign of this dispersion, you can make the entire optical line
dispersion is zero. The fiber used for this purpose is called a dispersion-compensated fiber (DCF: DisPersion Compe-
nsation Fiber).
DCF has a finer core diameter and a larger refractive index difference than standard 1.3pm zero-dispersion fiber.
DCF is also an important component of WDM optical circuits.
Thirteen Polarization Holding Fiber
Light waves propagating in optical fibers, because of the nature of electromagnetic waves, so, in addition to the basic single
mode of light waves, there are essentially two orthogonal modes of electromagnetic field (TE, TM) distribution. Usually, because
the structure of the cross-section of an optical fiber is circularly symmetric, the propagation constants of these two polarized modes are equal, and the two beams of polarized light do not
interfere with each other. In reality, however, the fiber is not completely circularly symmetric, for example, it has a curved section, and there is a binding factor between the two polarization modes, which are irregularly distributed on the optical axis. This variation in polarized light causes dispersion,
known as polarization mode dispersion (PMD). For cable television, which now focuses on distributing images, the effect is not yet significant.
But for some future ultra-wideband business with special requirements, such as: ① coherent communications using differential detection, to
seek a more stable polarization of the light wave; ② optical machines, such as the input and output characteristics of the input and output requirements and polarization; ③ in the production of the
polarization maintaining optocoupler and polarizer or de-polarizer, etc.; ④ the production of fiber optic sensitivities using optical interference,
Where polarization is required to maintain optocoupler, the polarization mode dispersion (PMD) is the main cause of dispersion, which is not very significant.
Where the polarization wave is required to remain constant, the fiber is improved to make the polarization state constant fiber is called Polarization Maintaining Fiber (PMF: Polarization Maintaining fiber), also known as fixed polarization
fiber.
XIV Birefringent fiber
Birefringent fiber refers to a single-mode fiber, can be transmitted orthogonal to each other, the two intrinsic polarization modes of optical
fiber. Because, the phenomenon in which the refractive index varies with the direction of polarization is called birefringence. In the method of causing birefringence
. It is also known as PANDA fiber, Polarization-maintai-
ning AND Absorption- reducing fiber. It is in the core of the transverse two, set the thermal
expansion coefficient of large, circular cross-section of the glass part. In the high-temperature fiber drawing process, these parts contract,
the result is that in the core y-direction produces tensile, and at the same time in the x-direction presents compressive stress. This results in a photoelastic
effect in the fiber, which causes a difference in the refractive index in the x- and y-directions. The polarization is kept constant by this principle.
Fifteen environmentally resistant optical fiber
Communication optical fibers usually work in ambient temperatures between -40 to +60 ℃, and are designed not to be exposed to a large
amount of radiation as a prerequisite. In contrast, optical fibers that can operate at lower or higher temperatures and in harsh environments where they can be subjected to high pressure or external
influence and exposure to radiation are called Hard
Condition Resistant Fibers (Hard
Condition Resistant Fibers).
Generally, in order to mechanically protect the surface of the fiber, it is coated with a layer of plastic. However, as the temperature rises,
the protective function of the plastic decreases, limiting the temperature at which the fiber can be used. If you change to heat-resistant plastics, such as poly
Tetrafluoroethylene (Teflon) and other resins, you can work at 300 ℃ environment. There are also quartz glass surface coating
Nickel (Ni) and aluminum (A1) and other metals. This type of fiber is called Heat Resistant Fib-
er.
Also, when optical fibers are exposed to radiant rays, the light loss increases. This is because when quartz glass is exposed to
radiation, structural defects (also called color centers: Colour Center) appear in the glass, especially at
0.4 to 0.7 pm wavelengths when the loss increases. The way to prevent this is to switch to quartz glass doped with OH or F elements, which can suppress the loss defects caused by radiation lines.
These fibers are called radiation-resistant fibers. This fiber is called radiation-resistant fiber (Radiation Resista-
nt Fiber), mostly used in nuclear power stations to monitor the use of optical fibers such as mirrors.
16 Seal Coated Fiber
In order to maintain the mechanical strength of the fiber and loss stability over time, the glass surface coated with inorganic materials such as silicon carbide (SiC), titanium carbide (TiC), carbon (C), etc., which is used to prevent the diffusion of water and hydrogen from the outside
The optical fiber manufactured by the HCF (Hermetically Coated Fiber): Hermetically Coated Fiber). Currently, it is common to achieve a full sealing effect by using a high-speed buildup of carbon layers in a chemical
Chemical vapor deposition (CVD) production process. This
Carbon Coated Fiber (CCF) effectively cuts off the fiber from outside hydrogen molecules. It has been reported to last up to 20 years in a room-temperature
hydrogen environment without increasing losses. Of course, it can slow down the fatigue process of mechanical strength by preventing the intrusion of moisture
and its fatigue coefficient (Fatigue Parameter) can reach over 200. Therefore, HCF is used in
harsh environment requiring high reliability of the system, such as submarine fiber optic cable is an example.
Seventeen Carbon Coated Fiber
Carbon Coated Fiber (CCF: Carbon Coated
Fiber) is an optical fiber in which a carbon film is coated on the surface of a quartz optical fiber. The mechanism is to use the dense film layer of carbon to isolate the surface of the fiber from the outside world, in order to improve the mechanical fatigue loss of the fiber
and increase the loss of hydrogen molecules.
CCF is a kind of sealing coating fiber (HCF).
18 Metal Coated Fiber
Metal Coated Fiber (Metal Coated Fiber) is an optical fiber coated with Ni, Cu, A1 and other
metal layers on the surface of the fiber. There are also coated with plastic on the outside of the metal layer, in order to improve the heat resistance and can be used for
electricity and welding. It is one of the optical fibers that are resistant to harsh environments and can also be used as a component of electronic circuits.
Early products were made by coating molten metal during the drawing process. Because of this method because of the glass and
Metal expansion coefficient difference is too large, will increase the small bending loss, the practical rate is not high. Recently, due to the success of the low-loss non-electrolytic coating method on the surface of the
glass fiber, the performance has been greatly improved.
19 Doped Rare Earth Fiber
In the core of the fiber, doped with how (Er), Chin (Nd), spectral (Pr) and other elements of the rare earth group
Fiber optics. 1985 in the United Kingdom's Sourthampton (Sourthampton) University of the Pace (Payne) and other first
first found that the doped rare earth elements of optical fiber (Rare Earth DoPed Fiber). Rare Earth DoPed Fiber) has the phenomenon of laser oscillation and light amplification
. Thus, from then on unveiled the veil of light amplification such as tragic bait, and now has been practical 1.55pm EDFA
is the use of bait-doped single-mode optical fiber, the use of 1.47pm laser excitation, to get 1.55pm optical signal amplification
large. In addition, an error-doped fluoride fiber amplifier (PDFA) is under development.
Twenty Laaman fiber
Laaman effect refers to a substance into a monochromatic light frequency f, in the scattered light will appear outside the frequency f
f±fR, f±2fR and other frequencies of the scattered light, a phenomenon known as the Laaman effect. This phenomenon is called the Raman effect because it is produced by the energy exchange between the molecular motion and lattice motion of matter
. When a substance absorbs energy, the vibration
momentum of the light becomes smaller, and the scattered light is called a Stokes line. On the contrary, from the matter to get energy, and
vibrational number becomes larger scattered light, is called anti-Stokes lines. Thus the deviation FR of the vibrational number, which reflects the energy level,
can show the value inherent in matter.
The optical fiber made from this nonlinear media is called Raman fiber (RF: Raman Fiber).
In order to enclose light in a tiny core for long-distance propagation, there is a light-substance interaction
effect that enables long-distance transmission without distortion of the signal waveform.
Coherent induced scattered light is obtained when the input light is enhanced. A device that applies induced Raman scattered light
A Raman fiber laser is available for use as a power source for spectroscopic measurements and as a power source for fiber dispersion testing.
In addition, the application of sensing Raman scattering as an optical amplifier in long-distance communication over optical fibers is being discussed.
Twenty-one Eccentric Fiber Optics
The core of a standard optical fiber is set in the center of the cladding, and the cross-sectional shape of the core and cladding is concentric.
But due to different uses, there will be core location and core shape, cladding shape, made into different states or cladding
layer perforation to form a heterogeneous structure. Relative to the standard optical fiber, these fibers are called shaped optical fiber.
Excentric Core Fiber (Excentric Core Fiber), which is a type of shaped fiber. Its core is set
in the off-center and close to the cladding outer line of the eccentric position. Because of the core's proximity to the exterior, some of the light field propagates through the cladding (called the Evanescent Wave).
So when a substance is attached to the surface of an optical fiber, the optical properties of the substance affect the light waves propagating through the fiber
. If the refractive index of the attached substance is higher than that of the fiber, the light wave is radiated out of the fiber. If the refractive index of the attached material
quality is lower than the refractive index of the optical fiber, light waves can not be radiated out, but will be subject to material absorption of light waves
loss. By utilizing this phenomenon, it is possible to detect the presence or absence of attached substances and changes in the refractive index.
Eccentric fiber (ECF) is mainly used as a fiber optic sensor to detect substances. Combined with the optical time domain reflectometer (OTDR)
test method, it can also be used as a distribution sensor.
Xxii Luminescent Fiber Optics
Optical fibers manufactured with fluorescent substances. It is an optical fiber in which a portion of the fluorescence generated when irradiated by light waves such as radiation and ultraviolet rays
can be transmitted through the closure of the optical fiber.
Luminescent fiber can be used to detect radiation and ultraviolet light, as well as for
wavelength conversion, or as temperature sensitizers and chemical sensitizers. It is also called Scintillation Fiber in the detection of radiation.
Luminescent optical fiber is being developed from the perspective of fluorescent materials and doping, plastic optical fiber.
Twenty-three Multi-core Fiber
The usual optical fiber consists of a core area and a cladding area around it. However, a multi-core fiber (Multi
Core Fiber) is a **** the same cladding area in the presence of multiple cores. Because of the proximity of the cores to each other
there are two functions.
One is a structure in which the cores are widely spaced, i.e., not optically coupled. This kind of fiber, due to the ability to improve the integrated density per unit area of the transmission
line. In optical communications, can be made into a ribbon cable with multiple cores,
and in the field of non-communication, as a fiber optic image beam, there will be made into thousands of cores.
The second is to make the distance between the cores close, can produce light wave coupling. The use of this principle is developing
Double fiber core sensitizer or optical loop device.
Twenty-four Hollow Fiber
The fiber will be made into a hollow, forming a cylindrical space, used for optical transmission of optical fiber, called hollow fiber
(Hollow Fiber).
Hollow fibers are mainly used for energy transmission for X-ray, ultraviolet, and far-infrared light energy transmission.
There are two types of hollow fiber structures: one is made of glass in the form of a cylinder, and its core and cladding principle is the same as that of the step-type.
The use of light in the air and glass between the total reflection propagation. As a result, most of the light can be propagated in the lossless air
with a certain distance propagation function. Secondly, the reflectivity of the inner surface of the cylinder is made close to 1 to reduce the reflection
Radiation loss. In order to improve the reflectivity, there is a dielectric inside the Jane, so that the operating wavelength band loss is reduced.
For example, it can be made to wavelength 10.6pm loss of a few dB / m.
This is the first time in the world that the wavelength of the product has been reduced.