Optical fiber communication-Presented by Kiran Devkota

Lumbini Net Pvt. Ltd.
Optical Fiber Communication
Kiran DevkotaApril 2nd 2014

Overview
• Fiber optics is a medium for carrying
information from one point to another in the
form of light.
• Unlike the copper form of transmission, fiber
optics is not electrical in nature.
• A basic fiber optic system consists of a
transmitting device that converts an electrical
signal into a light signal

Fiber Optic Materials
Silica Fibers
• Both core and cladding are of glass.
• Very pure SiO2 or fused quartz.
• Any other remaining impurities causes attenuation
and scattering
Plastic Fibers
•Plastic core and plastic cladding.
•Flexible and Light.
•Widely used in short distance applications
Plastic-clad Fibers
•Glass as core and plastic as cladding

Basic Construction of a Fiber Optic
Cable
Core
This is the physical medium that transports optical signals from an attached light
source to a receiving device. The core is a single continuous strand of high-purity
glass or plastic whose diameter is measured in microns
Cladding
This is a thin layer that is extruded over the core and serves as the boundary that
contains the light waves (more on this later), enabling data to travel through the
length of the fiber.
refraction index less than core

Basic Construction of a Fiber Optic
Cable
Coating:
This is a plastic coating over the cladding to reinforce the
fiber core, help absorb shocks, and provide extra
protection against excessive cable bends. It does not
have any effect on the optical waveguide properties,
though.
Strengthening fibers:
These components help protect the core against crushing
forces and excessive tension during installation.
Cable jacket:
This is the outer layer, or sheathing, of the cable

Total internal reflection
• phenomenon that happens when a propagating
wave strikes a medium boundary at an angle larger
than a particular critical angle with respect to the
normal to the surface

Advantage and Disadvantage
Advantage
• Enormous potential bandwidth
• Small size and weight
• Electrical Isolation
• Signal security
• Low transmission loss
• Potential low cost
Disadvantage
• It requires a higher initial cost in installation
• the connector and interfacing between the fiber optic costs a lot
• requires specialized and sophisticated tools for maintenance and
repairing

Types of Optical Fiber
Single Mode /Multimode
Single-mode fiber
• has a small core(8 to 9 microns)
• Keeps the light signals going farther before they need to
be beefed up, or amplified
• Used for long distance communication
• Transmit infrared laser light (wave length = 1310-
1650nm)

Multimode fiber
• Much larger core (50 or 62.5 microns )than
single-mode fiber.
• gives light waves more room to bounce around
inside as they travel down the path
used for short distance communication
• Transited infrared light (wave length = 850 –
1310nm ) from light emiting diodes (LEDs).

Single/Multi Mode Fiber

Attenuation
• The decrease in signal strength along a fiber
optic waveguide caused by absorption and
scattering is known as attenuation.
Attenuation is usually expressed in dB/km.
• Due to attenuation, the power output (Pout)
at the end of 1km of optical fiber drops to
some fraction (k) of the input power (Pin) i.e.
Pout = k.Pin (kless than 1).

Attenuation

Types of connector
LC
Lucent Connector, Little Connector, or
Local Connector

Types of connector
• FC
• Ferrule Connector or Fiber Channel
SC
Subscriber Connector [3] or
square connector [3] or
Standard Connector

Types of connector
Angle-polished connectors (APC) and Ultra-polished connetors (UPC)
• Insertion Loss
Insertion loss is defined as measurement for the amount of optical
power lost through a mated connector pair.
• UPC APC
0.2 dB max. 0.35 dB max.
0.09 dB typical 0.15 dB typical
• Return Loss
Return loss is a measurement of the light reflected back to the source
at anoptical interface
UPC APC
- 57 dB min -65 dB min.

SFP
The small form-factor pluggable (SFP) is a
compact, hot-pluggable transceiver

SFP
Part No. Package
Data
Rate
(bps/Hz)
Tx(nm)
Pout(d
Bm)
Sensitivity
(dBm)
Temp
°C
Reach
APS55123xxLB2 1.25G SFP 1.25G
1550nm
DFB
0~5 <-32 0~70℃ 120km
APS55123xxL80 1.25G SFP 1.25G
1550nm
DFB
0~5 <-25 0~70℃ 80km
APS31123xxL40 1.25G SFP 1.25G
1310nm
FP
-5~0 <-25 0~70℃ 40km
APS31123xxL20 1.25G SFP 1.25G
1310nm
FP
-9~-3 <-25 0~70℃ 20km
APS31123xxL2 1.25G SFP 1.25G
1310nm
FP
-15~-8 <-24 0~70℃ 2km
APS85123xxL05 1.25G SFP 1.25G
850nm
VCSEL
-9~-4 <-18 0~70℃ 550 meters

SFP
Transceiver Type: 100_BASE_LX_SFP
Connector Type: LC
Wavelength(nm): 1310
Vendor Name: Raisecom
Vendor Part Number: 03/SS135-D-R
Vendor Serial Number: 112130500711
Fiber Type: Single-Mode
Transfer Distance(meter): 15000
Transceiver Type: 1000_BASE_LX_SFP
Connector Type: SC
Wavelength(nm): 1550
Vendor Name: OEM
Vendor Part Number: APSB53123CDL40
Vendor Serial Number: SG53431400010
Fiber Type: Single-Mode
Transfer Distance(meter): 40000

SFP
Optical High Alarm High Warn Low Warn Low Alarm
Rx Power Threshold Threshold T hreshold T hreshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
----------------------------------------------------------------------------------------------------------------------------------------------------------
25 - 19.3 - 2.9 - 4.9 - 31.5 - 33.9
26 - 16.9 1.0 0.0 - 23.9 - 26.9
27 - 3.9 1.0 0.0 - 23.9 - 26.9
28 - 11.6 1.0 0.0 - 23.9 - 26.9
Optical High Alarm High Warn Low Warn Low Alarm
Tx Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
----------------------------------------------------------------------------------
25 - 11.8 - 4.9 - 7.9 - 14.9 - 17.9
26 - 5.2 - 0.9 - 1.9 - 10.0 - 10.9
27 0.5 5.0 4.0 - 2.9 - 3.9
28 0.6 5.0 4.0 - 2.9 - 3.9

Types of Optical Fiber Cable
• Distribution cables
• Loose tube cables

Types of Optical Fiber Cable
• Armored Cable:
• Aerial Cables

Loss in 0ptical Fiber Communication
• Loss Inherent to Fiber
Light loss in a fiber that cannot be eliminated during the
fabrication process is due to impurities in the glass and
the absorption of light at the molecular level
Splice Loss:
• Poor cleave
• Misaligned fiber cores
• Air gap
• Contamination
• Index-of-refraction mismatch
• Core diameter mismatch

Loss in 0ptical Fiber Communication
Connector Loss:
• Dirt or contaminants on the connector (very common)
• Improper connector installation
• Damaged connector faces
• Poor cleave
• Misaligned fiber cores
• Index-of-refraction mismatch solved by index matching gel
Bend Loss:
• Sharp curves of the fiber core
• Displacements of a few millimeters or less, caused by buffer or jacket
imperfections
• Poor installation practice
Fresnel Reflection:
if the end of a fiber has any kind of air gap, then some of the light traveling from
the air to the core, about 4%, is reflected back into the air instead of
transmitting/refracting into the core

Loss Calculation
• Fiber loss at the operating wavelength
Wavelength (nm) 850 1300 1310 1550
Fiber Atten. dB/km 3.5 1 0.3 0.25
• Connector Loss
0.3 dB
• Splice Loss
Mechanical connection 0.2
Fusion splicing 0.1

OTDR (Optical Time Domain Reflectmeter)
• OTDR is a measurement instrument for
identifying optic fiber transmission features.
• OTDR sends out a light pulse into connected optic
fiber, and receive reflections of events and
backward scattering power of pulse in time.
Events
• Events refer to any abnormal points causing
attenuation or sudden change of scattering
power besides the normal scattering of optic
fiber, which include all kinds of losses like
bending, connections and ruptures.

OTDR (Optical Time Domain
Reflectmeter)
Reflection Events
Reflection is primarily a problem with connectors but may also affect mechanical splice
Properly made fusion splices will have no reflection; a reflection peak indicates incomplete
fusion or inclusion of an air bubble or other impurity in the splice

OTDR (Optical Time Domain
Reflectmeter
• Non-reflection Events
• Non-reflection events happen at certain points where there is some optic loss but no light
scattering.
• When non-reflection event occurs, a power decline shows on trace.

OTDR
OTDR setup
• Range Length of optic fiber relevant to the trace
• Pulse Width of laser pulse sending out from OTDR to optic fiber. With
narrow pulse width, there will be higher resolution and smaller dead zone,
however, the dynamic range will be decreased
•
•
• Average Time To select suitable testing time. in case of measurement of long-
distance optic fiber, long average time should be selected in order to review events
at long-distance end
• Wave length To select laser wave length for measurement
• Measurement Mode To select mode for measurement. Averaging and Real time
mode
• VFL Power on or off visible
• Length Units To select length units

Tools
• Optical power meter (OPM)
used to measure the power in an optical signal. The term usually refers
to a device for testing average power in fiber optic systems
Fiber Optic Fault Locator
• used to locate the broken points of optical fiber, connector
inspection and tracing of fibers.
Optical fiber identifier
designed to detect optical signals without disrupting traffic
Optical Fiber cleaning

THANK YOU

Optical fiber communication-Presented by Kiran Devkota

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