TYPES OF FIBER

EVALUATION

Optical Fiber Mostly SM fiber is used long distance communication typically 5 Km to 170 Km with out any problemMM fiber is only used for the low data rates and short distance communication typically 100 meter to 1 KmDistance of reach depends on so many parameters

Typically SM FibersNormal Single Mode FiberDSF (Dispersion shifted fiber) NZ-DSF ( dispersion shifted fiber )DCF (Dispersion compensating fiber)LEAF (Larger effective area fiber)DFF (Dispersion Flattened Fiber)

Typically SM FibersDispersion is zero at 1312 nm wavelength At 1312 nm the losses in the fiber is highWhile Losses minimum at 1550 nm while the dispersion parameter is +17 ps/nm/Km

Typical SM Fiber ParametersZero dispersion wavelength (nm)Cutoff wavelength (nm)Attenuation (dB/Km)Dispersion (ps/nm Km)PMD coefficient (ps/Km1/2)Mode field diameter (micro meter)Effective area (micro meter2)

Typical SM Fiber ParametersParameter at different wavelengths areAttenuation slope (dB/Km/nm)Dispersion slope (ps/nm2 Km)Mode field diameter

Typical Value for SM Fiber

Sheet1

1Attenuation only in fiber (dB/km) 1550 nm0.25

2Attenuation vs. wavelength (dB/km)0.05

Max Delta from 1550nm value between(1525-1625 nm)

3Dispersion slope (ps/nm 2 -km) mean At 1550 (nm) 0.092

4Zero dispersion wavelength (nm)1310 or 1550

5Dispersion (ps/nm.km) mean @1550nm (P or N)

1530 to 1565 nm2.6 to 6.0 P

1565 to 1625 nm4.5 to 11.2 P

6Mode field diameter (m) At 1550 nm9.2 to 10

7Max Effective area (m2) Norminal72

8Cutoff Wavelength (nm)1247

9PMD Coefficient (ps/km1/2), max mean, @1550 nm0.08

10Effective Group Index of Refraction @ 1550 nm1.469

Sheet2

Sheet3

ITU Standards (Optical Fiber)G.650 Definition and test methods for the relevant parameters of single mode fibers G.651 Characteristics of a 50/125 m multimode graded index optical fiber cable G.652 Characteristics of a single-mode optical fiber cable G.653 Characteristics of a dispersion-shifted single-mode optical fiber cable.

ITU Standards (Optical Fiber)G.654 Characteristics of a 1550 nm wavelength loss- minimized single-mode optical fiber cable G.655 Characteristics of a non-zero dispersion single- mode optical fiber cable.

G652 fiberITU-recommendation G.652SMF hasZero chromatic dispersion at 1310 High chromatic dispersion (approx. 17ps/nm-km) at 1550nmAdvantage Support WDMLow in costDisadvantageSuitable only for short and medium distancesNeeds Dispersion Compensation modules

G652 fiber

Dispersion Shifted FiberITU-recommendation G.653Wave guide dispersion and material dispersion cancel out each other at 1310nmSame cancellation is used at 1550nm bandThe reasons are principally:Fiber attenuation is a lot lower in the 1550 nm bandErbium doped fiber amplifiers operate in this bandDone by increasing the waveguide dispersion

Dispersion Shifted Fiber (DSF)

Dispersion Slope of SM Fibers

Dispersion Components

Dispersion Shifted FiberAdvantageSuitable for DWDM applications, with broad channel spacingDispersion compensation is required after long distancesDisadvantageNot suitable for higher channel countSuffers from strong nonlinear effectsUnsuitable for narrow channel spacing, due to four wave mixing

Non Zero Dispersion shifted FiberITU-recommendation G.655Low positive value of dispersion (4 ps/nm/km in the 1530-1610 nm band)Advantages Minimizes unwanted effects Four-Wave-Mixing(FWM)More distance than SMFDisadvantageNot able to carry large optical power

Non-Zero Dispersion Shifted Fiber

Dispersion Flattened FiberHere dispersion over range from 1300 to 1700 is reduced i.e 3ps/nm/kmAdvantages Very less dispersion change within EDFA spectrumEfficient for DWDM systems with less number of channelsDisadvantagesExtremely high attenuation (2dB/Km)Severe Four Wave Mixing problems

Dispersion Flattened Fiber

Large Effective Area Fiber (LEAF) :

Large Effective Area Fiber (LEAF) :Fiber effective is increased to 72 to 80 micro meter2 from 50 micro meter2 This type of fiber can carry large amount of the optical powerNonlinear interactions will be reducedGenerally used in Undersea applicationsDisadvantageDifficult fiber designCost is very high

Fiber Technologies

This is the first generation of Single-mode fibers. Lot of fibers that were deployed in the 80s up to mid 90s fall under this category. We need to understand the feasibility and drawbacks of deploying DWDM on this type of fiber because there are still new projects being done based on them. As a recap, Zero chromatic Dispersion Wavelength 0 is the wavelength at which minimum or zero dispersion occurs. Erbium Doped Fiber Amplifier (EDFA) generally amplifies wavelengths in the range of 1530 to 1560 nm. This range is called the EDFA gain spectrum. This happens to be in the second window of operation and attenuation is less at this window. This is the most common type of fiber found at present. It has been extensively deployed during the 90s. This fiber reduced the effect of Four Wave Mixing (FWM). This has higher dispersion than DSF, thus reducing the effect of for wave mixing, but still has smaller dispersion than NDSF. Different manufactures have different values for the 0 of these fibers. This is the most suitable fiber type for the present DWDM systems where we have a large number of channel counts. Selection of the required type of fiber depends on a number of parameters, including the OSC (optical Service Channel) wavelength that is used. Dispersion flattened fibers where introduced in the market to minimize the effects of dispersion. It also has zero dispersion within the complete range of the EDFA gain spectrum.