Fiber optics by Eng. Geremew Tefera

1. Fiber optics
General issues

2. The most common causes of fiber optic malfunctions
 Broken fibers because of physical stress or excessive bending
 Insufficient transmitting power
 Excessive signal loss due to a cable span that’s too long
 Excessive signal loss due to a contaminated connector
 Excessive signal loss due to faulty splices or connectors
 Excessive signal loss due to having too many splices or connectors
 Faulty connection of fiber to the patch panel or in the splice tray
 The cable’s attenuation may be too high because of poor quality splices or too
many splices.
 Things like dust, fingerprints, scratches, and humidity can contaminate
connectors.
 There is low transmitter strength.
 There are bad connections in the wiring closet.

3. Cause of loss
 Each connector gives about a 0.5-db loss up to a maximum of about .75 dB.
 Each splice results in a loss of about 2 dB.
 If you’re using single-mode fiber, you can plan on losing 0.1 db for every 600
feet of cable.
 If you’re using multimode cable, plan on losing about 0.1 dB per 100 feet of
cable.

4. Common Fiber Optic Cabling Issues
 Fiber Damage
 Fiber optic cables make use of glass fibers to transmit data. And although these cables are made
to withstand natural elements, its glass fiber material makes it vulnerable to breakage or
damage. That’s why it’s important to be mindful of how you handle the cables you use for your
fiber optic network.
 In order for you to continue enjoying the benefits of fiber optics, you have to replace damage
fibers immediately. That’s why it’s recommended to make use of a fiber optic tracer to look for the
faults within the cable.
 Incorrect Connectors
 At present, there are different kinds of connectors available that you can use for fiber optic cords.
But before you purchase one, you have to see to it that you have the appropriate one for your
fiber optic cables. It’s important to have a connector that fits well on your cables to optimize your
fiber optic network experience. Moreover, you should also make sure that they are inserted
properly so that they won’t slip out.

5.  Length Problem
 When your fiber optic cable is longer than what’s necessary, it becomes susceptible to bending,
twisting, and winding around itself—these are potential risks that can cause permanent damage to
your cable. That said, it’s crucial to make sure that you’re using the appropriate length for your network
infrastructure. You can get the approximate length by measuring the distance between all the
equipment you’re going to connect using the fiber optic cables.
 Stretching Problem
 Another reason why fiber optic cables can get damaged is overstretching. When cables are stretched
over a certain range it can no longer tolerate, it can easily damage the components within it. To refrain
this from happening, you have to avoid pulling the jacket of the cable. If the need to fit or remove
connectors arises, it’s recommended to use a fiber optic grip tool. That way you’ll be able to perform
the necessary customization without the risk of stretching your fiber optic cables.
 External Damage
 When it comes to fiber optic cables, even the slightest splits and scratches can affect your network’s
performance. And that’s the exact reason why fiber optic experts can’t stress the importance of regular
cable inspections enough to fiber optic users.
 The possibility for external fiber optic cable damage is always present—that’s why it’s important to
keep an eye out for them. Once you spot any cable defects, remember to always replace these cables
for you to continue experiencing the business perks that fiber optics bring.

6.  Other Causes of Fiber Optic Problems
 Aside from the common fiber optic cabling issues mentioned above, there are other situations
that can cause fiber optic problems. And it’s important to identify them early to help you make the
complicated process of troubleshooting these network problems easier. The first step you can
take to do this effectively is to gather information. By doing this, you will be able to narrow down
the possible causes of your network problem and troubleshoot it more efficiently.
 To get you started, you can base your questions during your data gathering from these common
scenarios that cause fiber optic problems:

7. The Most Common Causes of Fiber Optic Failure:
 Broken fiber because of excessive bending
 A disconnected cable
 Signal loss due to a cable span that is too long
 Signal loss due to a bad connector
 Signal loss due to faulty splices or too many splices
 Inadequate transmitting power
 Faulty connection to the patch panel
 The Most Common Causes of an Intermittent Fiber Optic Connection:
• Installer allowed too much of a loss budget
• Dust, fingerprints, and humidity
• Scratches on connectors

8. How to Troubleshoot Fiber-Optic Cable
 Step 1
 Inspect the fiber-optic cable by following it along its length. Look for
obstruct the cable's optical fibers. Gently straighten any unnecessary
 Step 2
 Remove any objects resting on top of, or otherwise putting pressure on,
 Step 3
 Check for excess tension in the cable. Fiber-optic cables should have
causes stress on the fibers. Slacken any cables that are pulled tightly.
 Step 4
 Shorten cable spans that seem excessively long by placing connected
and using shorter fiber-optic cables.
 Step 5
 Identify any splits, rips or tears in the cable. Replace any damaged

9. Connection Troubleshooting
 Step 1
 Locate the point at which the fiber-optic cable connects to a device,
router, television or other piece of electronic equipment.
 Step 2
 Check the connection. If the connection is loose, firmly secure the cable
 Step 3
 Inspect the cable's connectors. Spray the connector with compressed
and foreign particles.
 Step 4
 Disconnect the fiber-optic cable and reconnect it to the device if simply
fails to remedy the problem.
 Investigate the point of access for any fiber-optic cable that enters your
Remove any foreign elements that could obstruct or place stress on the

10. Troubleshooting
 a. First determine if the problem is with one or all the fibers in the cable.
 If all fibers are a problem, there is a likelihood of a severe cable installation
problem.
 If all fibers are broken or have higher than expected loss, an OTDR will show
the location of the problem on longer cables but premises cables may be too
short and need physical inspection of the cable run.
 If the problem is caused by kinking or too tight a bend, the cable will have to
be repaired or replaced. Generally OSP cables will be spliced as in a
restoration and if the cable is a short OSP cable or a premises cable,
replaced.

11.  b. High loss fibers have several potential causes, but bad splices or terminations are the most
likely cause for field terminated cables.
 In some cases, using improper termination practices will result in high loss for all fibers, just as in kinking or
bending losses, not just one fiber.
 c. Cables with a fiber or fibers showing very high loss or no light transmission at all should be tested for
obvious breaks in the pigtail fiber or cable, generally at the splice or connector, with a visual fault locator or
OTDR if of sufficient length (>100m)
 d. Testing for high loss should start with microscope inspection of terminations for proper polish, dirt,
scratches or damage.
 e. If dirt appears to be the problem, clean the connectors and retest.
 f. If other connector damage is found on visual inspection, re-termination will probably be necessary.
Sometimes scratches can be polished out with diamond film by an experienced technician.
 g. Pre-polished splice connectors with internal splices will generally look OK when inspected with a
microscope unless damaged after installation. The most likely cause of loss with these connectors is high
splice loss in the internal splice. They can be tested with a visual fault locator coupled into the fiber at the
far end. High light loss will be seen as an illumination of the connector ferrule. Some connectors have
translucent backs hells and can be tested with a VFL coupled directly into the connector.
 h. If the reason for high loss is not obvious and the connectors are adhesive/polish style, the problem may
be a fiber break in the back of the connector. A VFL may help in finding fiber breaks, depending on the
connector style and the opacity of the cable jacket.
 i. Splice loss problems can be pinpointed during OTDR testing. Confirmation with a VFL should be done if
the length from the end of the cable is short enough (~2-3km) where a VFL is usable. The VFL can find

12.  j. High loss links where the excessive loss is only a few dB can be tested with
a FOTP-171 type single-ended test with a source and power meter.
 When tested in this manner, a high loss connector will show high loss when
connected to the launch cable connector but not when connected directly to
the power meter detector which picks up all the light from the fiber.

13. Comparison Chart
PARAMETER COPPER CABLE FIBER OPTICS
Working principle Data is transmitted in the form of electrical pulses. Signal transmission is accomplished in the form of
light pulses.
Composed of Copper wire Glass fiber
Cost Low High
Transmission speed Slow Fast
Attenuation More Less
Transmission range Short as compared to fiber optics Long as compared to copper cable
Size and weight Thick and heavy Thin and light
Reliability Less reliable More reliable
Power consumption Greater than 10 W per user. Around 2 W per user
Bandwidth Lower Higher
Lifespan 5 years 30 to 50 years
Noise immunity Low High

14. Definition of Copper Cable
 Copper cables are guided media composed mainly of copper wires that allow
transmission of data from an end to another.
 Copper cable due to its conductive nature widely used as a medium for data
transmission for the past 50 years.
 In copper cables, the data is transmitted due to the movement of electrons.
 This is the reason; copper cable allows data transmission in the form of
electrical pulses.
 Copper cabling is known as the most compatible element in case of electrical
equipment.
 When telephones were invented in 1876 then need of copper cables as
electrical conductors had increased considerably.
 Copper is material that possess excellent creep characteristics that prove
advantageous during cable connections.
 At the same time as compared to other metals copper exhibits corrosion
resistance property.

15. Advantages
 It possesses higher electrical conductivity.
 Copper cables are less expensive and has low maintenance cost.
 These are highly compatible thus is widely used with electrical equipment.
 It is extensively available.
 Disadvantage of Copper Cable
• These are less reliable.
• Data transmission speed of copper cables is high due to low bandwidth.
• It consumes more power.
• Less immune to noise and other interferences.

16. Definition of Fibre Optics
 Fiber optics allows the transmission in the form of light pulses.
 These are composed of one or more strands of glass or silica.
 These are basically dielectric waveguide that works at optical frequencies.
 Fiber optics utilizes the principle of Total internal reflection in order to
transmit electromagnetic energy in form of photons (light particles).
 Fiber optics is composed of glass core which is surrounded by a plastic
cladding having a lower refractive index as compared to the core.
 The figure below shows a typical fiber optics

17.  When we talk about a fiber optic system then it necessarily has a device to
convert an electrical signal into a light signal at the transmitting end.
 Furthermore, a device that takes the light signal and changes it into the
electrical signal at the receiving end.
 It utilizes wavelength near to the infrared range of spectrum that lies above
visible range hence is not identified with naked eyes.

18. Advantages
 Optical fiber cables are durable hence last for longer durations when installed.
 It possesses greater immunity to electromagnetic interference.
 Due to large bandwidth, a large amount of data can be transmitted through the
cable.
 Fiber optics allows secured data transmission.
 Due to thin structure and smaller diameter, these occupies less space and is light
in weight.
 Fiber optics has a much higher capacity as compared to copper cable.
 Disadvantages of Fiber Optics
• As these are fragile in nature (delicate) thus requires more protection in comparison
to copper cables.
• Installation cost of optical fiber cable is high and is difficult to install.
• The need for repeaters increases with distance.
• Excessive bending can easily deteriorate the cable.

19. Applications
 Copper Cable
1. These are widely used in electricity distribution systems and telecommunication
system.
2. Due to easily bending nature, these are widely used in automobile industry.
 Fiber Optics
1. In telephone systems and Surveillance cameras.
2. These are widely used in computer networks and submarines cable networks.

20. Thank you!