FIBER OPTIC TRAINING

TYPES OF FIBER OPTIC CABLES

2010-11-24T23:21:00.001-08:00

TYPES OF FUSION SPLICE MACHINE

2010-10-19T23:53:00.000-07:00

- CORE ALIGNMENT

Core alignment fusion splicers use multiple cameras to inspect the two cleaved fibers before fusing and allow for multiple axis movement of the fibers. This provides for precise fiber alignment, resulting in a typical splice loss of only 0.02dB. This level of precision is required for all singlemode fiber applications and also enhances performance of multimode fiber.

- CLAD ALIGNMENT

Clad alignment splicers also have multiple cameras but only allow for single axis movement of the fiber. Alignment is aided by a fixed v-groove. The typical loss for this type of splice is 0.05dB. Clad alignment splicers are best suited for multimode applications.

- HAND HELD

A revolution in splicing came about with the introduction of battery powered handheld fusion splicers. These popular devices are compact and portable, yet offer performance on a par with benchtop models. The Fitel S122C fusion splicer pictured here features a 14 second splice (high speed mode), built in shrink oven, and other desirable features. Handheld splicers are great for working in confined spaces and aerial applications. They are ideal for FTTx, LAN, backbone and long haul installations.

SINGLEMODE VS MULTIMODE

2009-12-01T00:55:00.000-08:00

A "mode" in Fiber Optic cable refers to the path in which light travels. Multimode cables have a larger core diameter than that of singlemode cables. This larger core diameter allows multiple pathways and several wavelengths of light to be transmitted. Singlemode cables have a smaller core diameter and only allow a single wavelength and pathway for light to travel. Multimode fiber is commonly used in patch cable applications such as fiber to the desktop or patch panel to equipment. Multimode fiber is available in two sizes, 50 micron and 62.5 micron. Singlemode fiber is typically used in network connections over long lengths and is available in a core diameter of 9 microns (8.3 microns to be exact).

Single Mode Fiber - Single mode fibers have small cores sizes; any power run through the cladding can be easily lost where fiber bends.

Advantages

Single mode fibers have an operating length of greater than five miles. They also have higher bandwidths than Multimode because of their lower fiber dispersion. Single mode fiber doesn’t have modal dispersion, modal noise, and other effects that come with multimode transmission; single mode fiber can carry signals at much higher speeds than multimode fibers. They are standard choice for high data rates or long distance span (longer than a couple of kilometers) telecommunications which use laser diode based fiber optic transmission equipment.

Disadvantages

Light from single mode fibers only travel down the center of the core. They also use laser diodes, which tend to be more complex and expensive than light emitting diodes (LEDs).Since single mode fiber’s core is so much smaller than a multimode fiber’s core, coupling light into single mode fiber requires much tighter tolerances than coupling light into the larger cores of multimode fiber. However, those tighter tolerances have proved achievable.

Single mode fiber components and equipment are also more expensive than their multimode counterparts, so multimode fibers are widely used in systems where connections must be made inexpensively and transmission distances and speeds are modest.

Multimode Fiber - The mode count depends on the size of the core and the numerical aperture. Because of the large core size, aligning spliced fibers is easier.

Advantages

Multimode fibers can use LEDs, which are cheaper and more durable than laser diodes. Power is also distributed into the core and cladding.

Disadvantages

Multimode fibers have an operating range of less than five miles. As the core size and numerical aperture increases, they also tend to lose bandwidth.

Questions

How do I know what type of fiber I need?
This is based on transmission distance to be covered as well as the overall budget allowed. If the distance is less than a couple of miles, multimode fiber will work well and transmission system costs (transmitter and receiver) will be in the $500 to $800 range. If the distance to be covered is more than 3-5 miles, single mode fiber is the choice. Transmission systems designed for use with this fiber will typically cost more than $1000 (due to the increased cost of the laser diode).

What is the difference between multimode and single mode fiber?
Multimode fiber has a relatively large light carrying core, usually 62.5 microns or larger in diameter. It is usually used for short distance transmissions with LED based fiber optic equipment. Single-mode fiber has a small light carrying core of 8 to 10 microns in diameter. It is normally used for long distance transmissions with laser diode based fiber optic transmission equipment.

Should I install single-mode or multimode fiber?
This depends on the application. Multimode fiber will allow transmission distances of up to about 10 miles and will allow the use of relatively inexpensive fiber optic transmitters and receivers. There will be bandwidth limitations of a few hundred MHz per Km of length. Consequently, a 10 mile link will be limited to about 10 to 30 MHz. For CCTV this will be fine but for high speed data transmission it may not be.

Single-mode fiber on the other hand will be useful for distances well in excess of 10 miles but will require the use of single-mode transmitters (which normally use solid-state laser diodes). The higher cost of these optical emitters mean that single-mode equipment can be anywhere from 2 to 4 times as expensive as multimode equipment.

What is the maximum distance fiber optic transmitters can operate at?
Normal transmission distances can vary from a fraction of a mile to 40 miles (60 Kilometers) or more. The maximum transmission distance depends on output optical power of the transmitter, the optical wavelength utilized, the quality of the fiber optic cable and the sensitivity of the optical receiver. In general single-mode based systems operate over longer distances than multimode systems.

I already have single-mode fiber installed, but I am only going a short distance. Can I use lower cost multimode equipment?
No. Multimode equipment will not launch (inject) enough light into a single-mode fiber since the light carrying core of this fiber is only 9 microns in diameter compared to 62.5 microns in diameter for multimode fiber. Unfortunately you must use single-mode equipment. If the fiber distance is short however, the cost for replacing the single-mode fiber with multimode fiber may be more economical than the higher cost for the single-mode electronics.

SPLICING PROCEDURE (PREPARATION)

2009-12-01T00:43:00.000-08:00

Fiber optic cable splicing procedure (How to splice fiber optic cable)

1. Strip fiber cable jacket. Strip back about 3 meters of fiber cable jacket to expose the fiber loose tubes or tight buffered fibers. Use cable rip cord to cut through the fiber jacket. Then carefully peel back the jacket and expose the insides. Cut off the excess jacket. Clean off all cable gel with cable gel remover. Separate the fiber loose tubes and buffers by carefully cutting away any yarn or sheath. Leave enough of the strength member to properly secure the cable in the splice enclose.

2. Strip fiber tubes. For a loose tube fiber cable, strip away about 2 meters of fiber tube using a buffer tube stripper and expose the individual fibers.

3. Clean cable gel. Carefully clean all fibers in the loose tube of any filling gel with cable gel remover.

4. Secure cable tubes. Secure the end of the loose tube to the splice tray and lay out cleaned and separated fibers on the table. Strip and clean the other cable tube’s fiber that is to be spliced, and secure to the splice tray.

5. Strip first splicing fiber. Hold the first splicing fiber and remove the 250um fiber coating to expose 5cm of 125um bare fiber cladding with fiber coating stripper tool. For tight buffered fibers, remove 5cm of 900um tight buffer first with a buffer stripping tool, and then remove the 5cm of 250um coating.

6. Place the fusion splice protection sleeve. Put a fusion splice protection sleeve onto the fiber being spliced.

7. Clean the bare fiber. Carefully clean the stripped bare fiber with lint-free wipes soaked in isopropyl alcohol. After cleaning, prevent the fiber from touching anything.

8. Fiber cleaving. With a high precision fiber cleaver, cleave the fiber to a specified length according to your fusion splicer’s manual.

9. Prepare second fiber being spliced. Strip, clean and cleave the other fiber to be spliced.

10. Fusion splicing. Place both fibers in the fusion splicer and do the fusion splice according to its manual.

11. Heat shrink the fusion splice protection sleeve. Slide the fusion splice protection sleeve on the joint and put it into the heat shrink oven, and press the heat button.

12. Place splice into splice tray. Carefully place the finished splice into the splice tray and loop excess fiber around its guides. Ensure that the fiber’s minimum bending radius is not compromised.

13. Perform OTDR test. Perform a OTDR test of the splice and redo the splice if necessary.

14. Close the splice tray. After all fibers have been spliced, carefully close the splice tray and place it into the splice enclosure.

15. Bidirectional OTDR test (or power meter test). Test the splices with an OTDR or power meter from both directions.

16. Mount the splice enclosure. Close and mount the splice enclosure if all splices meet the specifications.

FIBER OPTIC COLOR CODING

2009-10-05T03:20:00.000-07:00

Color code, used in fiber optics, resembles that of copper. the major difference is 12-color sequence as oppose to 10-color for copper. The sequence of colors is the same, with addition of two colors - Rose (11-th) and Aqua (12-th).

Fiber color codes are specified by TIA/EIA 598-A. in loose tube cables, this color code will be used for tubes as well as fibers within the tubes and subgroups

For cables that consist of more than 12 strands, the color code repeats itself. Each group of 12 strands is identified with some other means such as:

- Multiple buffer tubes each with 12 or less strands either numbered or colored following the same color code, e.g., 1st tube is blue, 2nd is orange, etc.

- 24 strand groups with the color code repeating with some variation, e.g., the 1st group of 12 strands are solid colors and the 2nd group are solid colors with a stripe or some other identifying mark.

FIBER OPTIC CABLE JACKET COLOR

For outdoor aerial and burial type cables, the jacket color is usually black polyethelene for both multimode and singlemode cables to prevent UV radiation damage.

For indoor cables, the outer most fiber cable jacket may be any color but the de facto industry standard is:

· Orange for multimode fibers

· Yellow for singlemode fibers

This is also generally true for fiber optic patch cords.

FIBER OPTIC CABLE

2009-09-25T02:08:00.000-07:00

Cable Components

The major components of a fiber-optics cable are the core, cladding, buffer strength, strength member and the jacket.

The core is made of glass or plastic. Plastic is easier to manufacture and use but works shorter distance than glass. The core can be anywhere from about 2 to several hundred microns (1 micron = 10-6m)

The core and cladding are actually manufactured as a single unit. The cladding is usually of plastic with a lower index of reflection than core.

Fiber cables are normally bundled with several cores e.g. 2, 4,6 ,8 ,12, 24, 36 or 72 (depends on manufacturing).

Different types and application

Indoor cables: Fire safety is the number one factor in selecting indoor cables, particularly those that run through plenum spaces. Indoor cables must pass the flame-retardant and smoke-inhibitor ratings specified by NEC.

Outdoor cables: Moisture resistance and temperature tolerance are the major factors when choosing materials for outdoor environment cables. They also need to be ultraviolet (UV) resistant.

Aerial/Figure 8 Self-Supporting Cables: Aerial cables must endure extreme temperature ranges from sunlight heat to freezing snow. They also must survive high wind loading.

FUNDAMENTALS OF FIBER OPTIC

2009-09-24T22:26:00.000-07:00

Fundamentals of Light Propagation in Light Guides

Fiber Optic light guides are media whose transverse dimension (diameter, thickness) can be very small, typically 10mm to 1 mm. They are very flexible and can be produced in virtually any desired length. The material is usually glass, quartz or plastic. For special applications, other exotic materials such as liquid light guides, sapphire, fluoride or calcogenide may be used. There are some unavoidable requirements for good light transmission, such as pure glass materials for the core and cladding and high transparency for the spectrum of interest. Minimal optical dispersion is also desired. Process parameters such as glass transformation temperature, viscosity, inclusions and chemical affinity dictate the economics and quality of the fiber product. Light launched into a fiber will after a given length reach the core material boundary and pass to another medium (glass, air, etc.). Depending on the incident angle, some of the energy will be refracted outward (leaky modes) and some will reflect back into the core material (Figure 2).

Fig 2.: Light transmission in Medium with n1 > n2

Maximum light can only be transmitted through the light guide if total internal reflection occurs at the core clad interface. In this case, b > bMin, where b Min is the angle of incidence for which b’ = 90°.

The light guide has a cladding material n2 ; n .. Index of refraction for the coupling medium (usually air; n = 1)

Propagation Mode

A fiber core is fairly thick relative to a wavelength of light and allows the light to enter it many difference angles. There are a finite number of angles at which the rays reflect and propagate the length of the fiber. Each angle defines a path or a mode.

There are basically two modes of a transmission in a fiber. A multimode fiber has a number of paths in which light ray may travel. A singlemode has a light ray in one direction only

Fiber are further classified by the refractive index profile of their core. They can be either step index or graded index. Three main types of fibers are multimode grades index and single mode fiber.