Data Communications And Network Management Biology Essay

Submitted to

Sri Lanka Institute of Information Technology



In partial fulfilment of the requirements for the

Bachelor of Science Special Honour’s Degree in Information Technology

February 2013


I certify that this report does not incorporate without acknowledgement, any material previously submitted for a degree or diploma in any university, and to the best of my knowledge and belief it does not contain any material previously published or written by another person, except where due reference is made in text.




Table of contents

1. Introduction (1)

1.1 Transmission in an optical fibre (2)

1.2 Advantages of fibre optics (2)

2. Fibre Optic Connector Types (3)

2.1 Fibre optic connectors (3)

2.2 Fibre optic connectors and splice loss mechanisms (3)

3. Connector types (5)

3.1 ST-style connector (5)

3.2 SC Duplex connector (6)

3.3 Small form factor connectors (7)

3.3.1 The MT-RJ connector (7)

3.3.2 The LC connector (8)

4. Connector ferrule shapes and polishes (9)

5. More fibre optic connector types in details (10)

6. References (13)


Table of figures

1.Figure 1.1:Fibre optic layout (1)

2.Figure 1.1.1:Fibre transmission (2)

3.Figure 2.2.1: Fibre optic connectors and splice loss mechanisms (4)

4.Figure 3.1.1:ST-style connector (5)

5.Figure 3.2.1:SC Duplex connector (6)

6.Figure connector (7)

7.Figure connector (8)

8.Figure 4.1: Connector ferrule shapes and polishes (9)


Fibre optics

1. Introduction

Long, thin strands of pure glass which has a diameter of a human hair are known as Fibre optics. They are used to transmit light signals over long distances. They are arranged in bundles and known as Optical cables.

There are three parts in a fibre optic.

The core – it is the thin glass centre of the fibre where the light travels.

The cladding – it is the outer optical material surrounding the core that reflects the light back into the core.

The buffer coating – it is the plastic coating that protects the fibre from moisture and damage.

Electronic Parts Image Gallery

Figure 1.1:Fibre optic layout

There are two types of optical fibres.

Single-mode fibres – they have small cores and transmit infrared laser light.

Multi-mode – they have large cores and transmit infrared light from Light Emitting Diodes.


1.1 Transmission in an optical fibre

In a fibre optic, light travels through the core by constantly bouncing from the cladding. This incident is known as Total Internal Reflection. The light wave can travel long distances since the cladding does not absorb any light from the core. But, due to impurities in the glass, some of the light signal degrades within the fibre. The extent that the signal degrades depends on the wavelength of the transmitted light and the purity of the glass.

Figure 1.1.1:Fibre transmission

1.2 Advantages of fibre optics

Less expensive – long cables can be made at a cheaper price compared to copper wires.

Thinner – can be drawn through holes which have very small diameters compared to copper wires.

Less signal degradation

No interference – since optical fibres use light signals other than electrical signals, they do not interfere with those of other fibres in the same cables.

Low power – lower power transmitters can be used other than high voltage electrical transmitters because optical fibres degrade less.

Digital signals – ideal for computer networks because they are suited for carrying digital information.

No fire hazards




2.Fibre Optic Connector Types

2.1 Fibre optic connectors

Because there are many choices today, selecting the right connector for your needs can be complicated. When selecting the best fibre optic connector for any installation, we have to consider about how efficient and cost-effective the task is done.

2.2 Fibre optic connectors and splice loss mechanisms

Connector and splice loss is caused by many factors. When the two fibre cores are identical and perfectly aligned and no dirt is present, the loss is minimized. What is propagated will only be the light that is coupled into the receiving fibre’s core.

There are two problems caused by End gaps. They are insertion loss and return loss. The emerging cone of the light from the connector will spill over the core of the receiving fibre and be lost. And also there is a refraction caused by the air gap between the fibres because of the change in refractive index from the glass fibre to the air gap. This phenomena is referred to as Fresnel refraction. Also it is called Back refraction or optical return loss. It can cause problems in laser based systems.

To minimize this back refraction, connectors use a number of polishing techniques. When it comes to mechanical splices, it is possible to reduce the back refraction by using non-perpendicular cleaves. It makes the back refractions to be absorbed in the cladding of the fibre. In order to minimize loss, the end finish of the fibre must be properly polished. It the surface is rough, it will scatter light and dirt can absorb light. Typical airborne dirt can be a major source of loss since the optical fibre is so small. At times when the connectors are not terminated, they should be covered to protect the end of the ferrule from dirt. Since the oils on human skin attract dirt, we shouldn’t touch the end of the ferrule. It is advisable to clean the connectors with lint-free wipes moistened with isopropyl alcohol before any connection and testing. Two sources of loss are directional. Numerical aperture (NA) and core diameter. Because of the differences in these two, they create connections that have different losses depending on the direction of light propagation. Transmission from a larger NA fibre to a smaller NA fibre will cause a greater loss than the vice versa because light from a larger NA fibre will be more sensitive to angularity and end gaps. But at the same time connecting a


small diameter fibre to larger one will gain minimal loss because it is less sensitive to end gaps or lateral oddest.

These fibre mismatches occur for two reasons. They are, the occasional need to interconnect two dissimilar fibres and production variances in fibres of the same nominal dimensions. Connecting a smaller fibre to a larger one gives minimal losses, but connecting a larger fibre to a smaller one will result in substantial losses.

fiber optic cable

Figure 2.2.1: Fibre optic connectors and splice loss mechanisms


3. Connector types

Today, there are two primary legacy optical fibre connector types and two primary small form factor(SFF) connectors used in local area networks(LANs). They are ST-styles & SC Duplex, and MJ-RJ & LC respectively. For several years these four types of connectors have a reputation for the performance and reliability desired for local area networks.

3.1 ST-style connector

The ST-style connector is also referred to as the BIFOC connector. This is a simplex fibre connector, that means one fibre in one ferrule. Four connectors and two adaptors are required to get a duplex ST-style connection. The ST housing includes a push and twist, spring loaded latching mechanism. It is relatively large when comparing to today’s standards, especially when consideration for "finger space" is considered. The ST-style connector was one of the first high performance, robust optical fibre connectors. ST-style connector is still a very popular optical fibre connector.

ST connector

Figure 3.1.1:ST-style connector


3.2 SC Duplex connector

Although ST-style is a completely functional connector, some of its properties are not well suited for the LAN market. A simplex connector is less desirable than a duplex connector because most LANs are based on duplex optical fibre. Because of this reason, the SC Duplex was introduced. The SC Duplex housing is completely different while the base component is the same as the ST-style. SC connector has a housing has a push-pull latch mechanism. That makes it easier to mate and de-mate and reducing the finger space needed. The SC connector is also referred to as the TIA586A connector. It consists of two SC connectors yoked together which can be both mated or de-mated with the same push or pull action. Because of these features, the SC Duplex became the connector in LAN standard internationally.

Figure 3.2.1:SC Duplex connector


SC Duplex


2.5mm cylindrical

2.5mm cylindrical

Ferrule type



Duplex connector?


Yes (yoke)

Latching type

Push and twist


Table 3.1:Comparison between ST-style and SC Duplex


3.3 Small form factor connectors

Although some of the LAN related issues for fibre connectivity was solved by SC Duplex, it couldn’t solve the density issue. The fibre connection density was still twice that of regular copper terminals (RJ 45) because of the single fibre ferrules, the large housings, and the finger space. Because of these issues, the industry really needed a duplex fibre connector that has the same basic size as RJ 45 connector.

3.3.1 The MT-RJ connector

The MT-RJ connector was developed with a single, two fibre ferrule recognizing that fibre spacing was the limiting factor in fibre connection density. The ferrule itself has a rectangular cross-section with two fibres spaced 700 μm apart and two guide pin holes which made the MT-RJ, the small form factor connector with the highest fibre density. The housing of the MT-RJ was made slightly smaller than the RJ-45 so that an MT-RJ connector can fit in the same port space as an RJ-45. It also has RJ-45 style latch, so it’s easy to mate and de-mate as an RJ-45 plug.

mtrj connector kitmtrj connector

Figure connector


3.3.2 The LC connector

Instead of the 2.5mm ferrule, the LC connector was developed using a reduced diameter and simplex fibre ferrule. The smaller ferrule allows for a smaller housing and results to a smaller connector. The latching mechanism of the LC connector is also similar to the RJ-45 connector.

LC connector

Figure connector




2.5mm *4.5mm rectangular

1.25mm cylinder

Ferrule type



Duplex connector?


Yes, with yoke

Latching type

RJ latch

RJ latch

Single ferrule



Smallest size (Duplex)



Plug and jack model?



GbE complaint?



Table 3.2:Comparison between MT-RJ and LC


4. Connector ferrule shapes and polishes

Fibre optic connectors can have different ferrule shapes or finishes. They are usually referred to as polishes. Early connectors had an sir gap between the connectors to prevent them rotating and grinding scratches into the ends of the fibres because they did not have keyed ferrules and could rotate in mating adapters.

fiber optic Connectors

Figure 4.1: Connector ferrule shapes and polishes

The connectors were designed to contact tightly which are now called Physical Contact (PC) connectors. It began with ST and FC which had keyed ferrules. The loss and the back reflection was reduced because the air gap was reduced. PC connectors had typical loss of 0.3dB and return loss of 30-40 dB while air gap connectors had losses of 0.5dB or more and return loss of 20dB.


5.More fibre optic connector types in details

Short name

Long form

Coupling type

Ferrule diameter


Typical applications

Avio (Avim)

Aviation Intermediate Maintenance


Aerospace and avionics



2.5 mm

Measurement equipment



2.5 mm




2.0 mm

Telecom in the 1970s and 1980s, obsolete

Deutsch 1000


Telecom, obsolete



IEC 61754-3

Telecom in Germany in 1990s; measurement equipment; obsolete



2.5 mm

Printed circuit boards

E-2000 (AKA LSH)

Snap, with light and dust-cap

2.5 mm

IEC 61754-15

Telecom, DWDM systems;


push-pull type

IEC 1754-8

Telecom & CATV networks


Enterprise Systems Connection

Snap (duplex)

2.5 mm

IBM mainframe computers and peripherals


2.5 mm

Japanese Industrial Standard (JIS)

LAN, audio systems; for 200 μm fibers, simple field termination possible, mates with ST connectors


Snap, with light and dust-cap

1.25 mm

IEC 61754-20

Fiber To The Home (LC Compatible)


Ferrule Connector or Fiber Channel


2.5 mm

IEC 61754-13

Datacom, telecom, measurement equipment, single-mode lasers; becoming less common


Snap, with dust-cap

1.25 mm

Backplane connector



3.175 mm

IEC 60874-2

Datacom, telecom, test and measurement


Lucent ConnectorLittle Connector, or

Local Connector


1.25 mm

IEC 61754-20

High-density connections, SFP transceivers, XFP transceivers




2.5 mm




1.25 mm


PC or APC configurations (note 3)


Snap, with light- and dust-cap

IEC 61754-23

High-density connections; rarely used


Media Interface Connector


2.5 mm

Fiber distributed data interface (FDDI)


Multiple-Fiber Push-On/Pull-off

Snap (multiplex push-pull coupling)

2.5×6.4 mm

IEC-61754-7; EIA/TIA-604-5 (FOCIS 5)

SM or MM multi-fiber ribbon. Same ferrule as MT, but more easily reconnectable. Used for indoor cabling and device interconnections. MTP is a brand name for an improved connector, which intermates with MPO.


Mechanical Transfer

Snap (multiplex)

2.5×6.4 mm

Pre-terminated cable assemblies; outdoor applications[


Mechanical Transfer Registered Jack or Media Termination - recommended jack

Snap (duplex)

2.45×4.4 mm

IEC 61754-18

Duplex multimode connections


Miniature unit


1.25 mm

IEC 61754-6

Common in Japan



2.0 mm

Common in Japan telecom in 1980s


Snap (duplex)



Plastic fiber, obsolete

OptoClip II

Snap (push-pull coupling)

None - bare fiber used

Proprietry Hüber & Suhner

Datacom and telcom; not common


Subscriber Connector or

square connector or

Standard Connector

Snap (push-pull coupling)

2.5 mm

IEC 61754-4

Datacom and telcom; GBIC; extremely common

SMA 905

Sub Miniature A


Typ. 3.14 mm

Industrial lasers, military; telecom multimode


SMA 906

Sub Miniature A


Stepped; typ. 0.118 in (3.0 mm), then 0.089 in (2.3 mm)

Industrial lasers, military; telecom multimode


Sub Miniature C


2.5 mm


Straight Tip]/Bayonet Fiber Optic Connector


2.5 mm

IEC 61754-2

Multimode, rarely single-mode; APC not possible (note 3)


Toshiba Link


most common is JIS F05

Digital audio




1053 HDTV

Broadcast connector interface

Push-pull coupling

Industry-standard 1.25 mm diameter ceramic ferrule

Audio & Data (broadcasting)



Snap (Duplex) Push-pull coupling

Industrial and electric utility networking; multimode 200 μm, 400 μm, 1 mm, 2.2 mm fibers