OTDR(OPTICAL TIME DOMAIN REFLECTOMETER)

OPTICAL TIME DOMAIN REFELCTOMETER

Table of Contents
• Wavelength Basics
• Optical Fiber Communication System Basics
• OTDR Fundamentals
• Trace Analysis
• DEVISER AE Series OTDR

Wavelength Basic
Short wavelength Long Wavelength

WL Band Wavelength SMF MMF
B Band 850nm － ●
O Band
1300nm － ●
1310nm ● －
S Band 1490nm ● －
C Band 1550nm ● －
１c&3 wavelength Node ＴＶ
ONU ＰＣ
TV
DAT
A
FWDM FWDM
1550nm
1310nm
1490nm
Optical Fiber Communication System

Power budget and Transmission design
OLT ONU
Receiving side：0～-18dBmTransmission side：-4～-9.5dBm
1. Power budget is the difference between the smallest output in the
transmission side and the smallest sensibility in the receiver side.
worst value by devices
Ex.
Power budget＝-9.5－(-18)=8.5dBm

②When confirming the power budget value, make the confirmation
for the transmission line design
Connector Fusion Splice Connector
OLT ONUTransmission Distant：2500m
Condition
① Connector loss：0.5dB/1point
② Splicing loss ：0.2dB/1point
③ Fiber transmission loss：0.35dB/km（1310nm）・ 0.20dB/km（1550nm）
Attenuation
① Connector ：0.5dB×2 points＝1.0dB
② Splicing loss : 0.2dB×1 point＝0.2dB 2.075dB
③ Fiber transmission loss：2.5km×0.35dB＝0.875dB
●For the value of Power budget「8.5dBm」, the attenuation of optical
transmission line is 「2.075dB」, no problem for this low value .
Power budget and Transmission design

Link Budget depends on the attenuation while transmitting the
signal in the optical fiber.
●The less optical attenuation is, the far transmission distance of
optical signal can.
The Factor of Loss

●Connection Loss
When fibers connecting, the light enter from (P1) to (P2) there some losses will
be occur whether it connected through splice or connector.
P1
P2
［d B］L=－10log
10
Entering Light Power
P1
Outgoing Light Power
P2
LOSS(dB) Transmittance(％)
０．０１０．９９８
０．０５０．９８９
０．１００．９７７
０．２００．９５５
０．３００．９３３
０．４００．９１２
０．５００．８９１
１．０００．７９４
→ Fusion Splicing(Avg.)
→ Connector Loss(Avg.)
→ Connector Loss(Max.)

●Return Loss
P3（Return Loss）
Entering Light Power
P1
Outgoing Light Power
P2
Connected
Face P1
L=－10log
P3
［d B］
Fresnel reflection is due to the light reflecting off a boundary
of two optical mediums, each having a different refractive
indexes (IOR).
Medium RI
Vacuum 1.0
Air 1.0003
Water 1.3
Silica(Fiber) 1.5
Diamond 2.4

Dirty Connectors End Face
①：The hand oil bonds the end-face
When doing the splice operation, touched the
connector tip. Or get dirty on the end face of
connectors by touching the skin.
②：The dust bonds the end-face
When doing splice operation, dropped the
connectors or get dirty on the end face of
connector by touching the clothes etc..
③：The Alcohol blot bonds the end face
When doing splice operation, cleaned the end
face by alcohol but left the alcohol mark after
drying. So having to clean the end face skillfully
and carefully.
●The state of connector end face after cleaning
by using the special cleaning tool.

• What is an OTDR?
- Optical time domain reflecto-meter
- Detect faults in an optical fiber link of a
communication network
《Application》
Fiber Distance Measurement
Event Loss measurement
Return Loss Measurement
Use OTDR to measure transmission loss
COPL_CONFIDENCIAL

Flowing
OTDR Theory
Expression
Receiving
light
Electric
Signal
Ele
Sig
（APD）
Directive
CouplerOptical
Signal
LightSource
(LD)
ctric
nal
Pulse
Generator
Optical
Signal
Set Parameter
SELECTING MODE
Measuring
Save Data
POWER ON

Reflection Loss:
Change of Refractive Index
Due to Back scattering – Reflection will too higher

OTDR SETUP
• Distance
• Pulse Width
• Acquisition Time

Distance
• Scales the graph
• Set to at least 1.5x distance
Shorter Distance 1.5x Distance

Pulse Width
Noise
Widen the pulse width→The measurable distance will be gotten along,
but can not recognized the near connected point.
Narrow the pulse width→The OTDR Can recognize connected point, but the
measurable distance will be not gotten along.
Below graph shows the measured result for 40km fiber in 5µs and 100ns pulse width.
• If set the pulse without suitable width , the waveform will be out of shape and the
event will not detect.
• Also it can increase noise in the waveform
Trace with 5µs Pulse Width Trace with 100ns Pulse Width

Acquisition Time
• Longer the Time can reduce the Noise.
• Longer the time can read event properly.

Recommended Setting
DISTANCE(km) PULSE WIDTH ACQ. TIME Launch CABLE
LENGTH(m)
<1.5 5/10ns 30/15s 150~300
1.5 ~ 5 10/30ns 30/15s 150~300
5~10 10/30ns 45/30s 150~300
10~20 30/100ns 45/30s 150~300
20~40 100/275ns 60/45s 150~300
40~80 275ns/1µs 90/60s 500
80~120 1µs/2.5µs 90/60s 500
120~160 2.5µs/10µs 120/90s 500 ~1k
160~200 10µs/20µs 120/90s 2.2k
200~260 20µs 120s 2.2k
NOTE: PULSE WIDTH may vary according to ratio of splitter used in Fiber Link

Auto Mode
• OTDRs have an “AUTO Mode” also.
• In Auto Mode OTDR Will automatically select Pulse Width &
Distance which is best suitable to reach end of the Fiber Link.
• In auto mode it may not provide the best result and on every trace it
may show the different result.

Loss Detail
1310nm – 0.33db/km
1550nm – 0.22db/km

DYNAMIC RANGE
The dynamic range is an important characteristic since it determines how far
the OTDR can measure.
Wavelength 1310/1550nm 1310/1550nm 1310/1550nm
Dynamic Range 29/27dB 30/28dB 34/32 dB
Typical
maximum
OTDR
measurement
range
70~90KM 80~100KM 120~140KM
Note : Actual OTDR measurement range depends upon the actual fiber and event loss in the
network.
COPL_CONFIDENCIAL

DEAD ZONE
• A dead zone is defined as the
length of time during which the
detector is temporary blinded by a
high amount of reflected light, until
it recovers and can read light again
DEAD ZONE
EVENT DEAD
ZONE (EDZ)
ATTENUTION
DEAD ZONE (ADZ)
COPL_CONFIDENCIAL

Dead Zone according to Pulse Width

• Sampling Resolution – it is the distance between two consecutive
sampling point

Micro-Bend
To detect micro-bend , trace on 1310nm & 1550nm both.

Transmitter Receiver
Transmission Distant：2500m
1550 & 1490nm
1310nm
1550/1310nm
APD / Laser BURN if signal trace on live Signal

Transmitter Receiver
Transmission Distant：2500m
1550 & 1490nm
1310nm
1625nm
Trace Over Live Signal

ADDITIONAL Features:
1. Laser Source
2. Optical Power Meter
3. Visual Fault Locator
4. QAM MODULE(Only in AE2100AQ Model)
5. Remote Access through Software

Laser Source
Laser
Source
Power
Meter
1310nm/1550nm/1625nm
Note:1625nm will be only in LIVE OTDR

Visual Fault Locator
A visual fault locator is a visible red laser designed to inject visible light energy into a
fiber sharp. Sharp bends, breaks , Faulty Connectors or other faults will leaks red light.

POWER METER
Measurement Range : +26 _-50dBm

Optional Features
Fiber path
Worker
Seeker
Fiber Inspection Probe
USB Wi-Fi Module

Beginning of trace event End of trace event
Connector/coupler event
Fusion splice event
Macro bend
Splitter
Fiber Path - Symbol
1:2 – 3~6dB
1:4 – 6~10dB
1:8 – 10~13dB
1:16 – 13~16.5dB
1:32 - >16.5

Maintenance: The user
creates fiber links, sets
parameters, and conducts
measurements according to
the link's readings.
Diagnosis: Once you have
tested a fiber link and
accepted the results, you
can test the link again and
compare the new result to
the saved one
WORKER

Detectable fiber length: ≤150km
A
Fiber B
SEEKER

OTDR(OPTICAL TIME DOMAIN REFLECTOMETER)

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