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INDIA October 6, 2003

Sterlite Optical Technologies LtdMixing of G655 and G652 Fibers in a Network

Confidential October 6, 2003

Discussion Outline

There are various points to consider while mixing NZDSF (G655) with standard SMF (G652):

� Joint Loss

� One Way OTDR anomaly

� Link Chromatic Dispersion

� Link Dispersion Slope

� Cutoff Wavelength

� Non linear effects.

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Confidential October 6, 2003

Optical Fiber Parameters

≤ 12600.080178010.5SMF (G652)

≤ 12600.0454.0528.3NZDSF (RS) (G655)

≤ 14800.0854.5729.4NZDSF (LEA) (G655)

Cable Cutoff(nm)

Slope (Ps/km/nm2)

D1550

(ps/nm*km)

Effective area (µm2)

MFD (µm)

Confidential October 6, 2003

Joint Loss

� The joint loss can be influenced by difference in their Mode Field Diameters(MFD) and refractive index profiles

� The loss due to joining fiber of two different MFDs can be calculated by

Loss(dB) = -20log[(2MFD1*MFD2)/(MFD12 + MFD2

2)]

� MFD manufacturing Tolerances is ± 0.4 µm. which gives joint loss of 0.008dB

Single Fiber Fusion Splice Loss(dB) at 1550nm

0.077G655 Reduced slope (RS)

0.035Standard SMF (G652)

Calculated added LossG655 Large Effective Area(LEA) to

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Confidential October 6, 2003

One Way OTDR Anomaly

� Principle of OTDR measurement depends upon the MFD of the fiber

� OTDR gives anomalous reading while measuring the joint which having two different fibers of different MFDs.

� The error is calculated by

OTDR Error (dB) = 10log[MFD2/MFD1]

� This shows that OTDR error are very large in compare to true splice loss

� True Joint loss is obtained by averaging the results of the two OTDR measurements

±0.49G655 (RS)

±0.48G652

One Way Error(dB)Splice of G655 (LEA) to

Confidential October 6, 2003

Link Chromatic Dispersion

� Chromatic Dispersion of among the single mode fibers are different

� Dispersion coefficient of mixed fibers is calculated by

Dmix = (DG655xLG655 + DG652xLG652)/(LG655+LG652)

Where, D = Dispersion Coefficient at predetermine wavelengths

L = Length of fiber used in networking

6017G652

2604.0G655 (RS)

2304.5G655 (LEA)

Dispersion Limited Distance at 10Gb/s (Km)

D1550

(ps/nm*km)

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Confidential October 6, 2003

Link Chromatic Dispersion

� A route containing a mixture of two fibers will have a distance limit between the either one

� This is the one way of looking on the selection of DCF module

Confidential October 6, 2003

Link Dispersion Slope

� Dispersion Slope of different single mode fibers are not same.

� Dispersion Slope of mixed fiber link can can be calculated by: -

Smix = (SG655xLG655 + SG652xLG652)/(LG655+LG652)

Where, S = Slope of given fiber at predetermined wavelength

L = Length of given type of fiber

� Relative Dispersion Slope (RDS) of mixed fiber is determined by

RDSmix = Smix/Dmix

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Confidential October 6, 2003

Link Dispersion Slope

� Ideally RDS of DCF module should be identical to the RDS of transmitted fiber

0.01True wave RS fiber DCF

0.0064NZDSF DCF

0.0035Wideband DCF

0.0022Standard DCF

0.0035SMF (G652)

0.02NZDSF (RS) (G655)

0.01NZDSF (LEA) (G655)

RDS (1/nm)

Confidential October 6, 2003

Link Dispersion Slope

� By calculating through above formula.

� RDS (Relative Dispersion Slope) of mixed fiber comprise of 60Km of SMF (G652) and 40 km of NZDSF (LEA) (G655) is 0.0058 which is almost identical to RDS of NZDSF DCF 0.0064

� It helps us to choose different DCF module

� Lengths of the different fiber for mixing can be calculated forparticular DCF module.

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Confidential October 6, 2003

Cutoff Wavelength

� ITU recommended cable cutoff of different Single mode fiber

� Since all WDM system (CWDM and DWDM) is optimized for C band (1530 – 1565nm) and L band (1565 – 1625nm), and also the attenuation at these wavelength is less compare to O band (1310 – 1350nm)

� The present and future networking is moving towards C and L band, for this G655 (LEA) is compatible with SMF (G652)

≤ 1260nmNZDSF (655) (RS)

≤ 1480nmNZDSF (655) (LEA)≤ 1260nmStandard SMF (G652)

Cable Cutoff

Confidential October 6, 2003

Non-Linear Effects

� Nonlinear effects mostly depend upon Effective area of the fiberhence it depend upon its MFD

� Non linear Effects ∝ 1/effective area

� NZDSF(LEA) has high effective area then other NZDS Fiber, so it is most compatible with SMF (G652)

� Nonlinear effects is complex interaction of different parameters, so detail computer simulations are generally performed to assessfiber performance with a given transmission system

8.352NZDSF G655 (RS)

9.472NZDSF G655 (LEA)

10.580SMF G652

MFD (µm)Effective area (µm2)

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Confidential October 6, 2003

Conclusion

� While mixing NZDSF (G655) with standard SMF (G652) following points are considered. 1.Joint Loss 2.One Way OTDR anomaly 3.Link Chromatic Dispersion 4.Link Dispersion Slope 5.Cutoff Wavelength and 6.Non linear effects.

� Out of six the top five are quantified,except Nonlinear effects which further reduced by using high effective area NZDSF (LEA), and by detail computer analysis.

� With the mixing of G655 with G652 we have advantage of dispersion and dispersion slope over pure G652 cable, which provides longer span length for regenerator with large operatingwindow.

� Mixing of different fiber has slightly higher splice loss then same fiber

Confidential October 6, 2003

Salaj Sinha, Associate General Manager – Technical Sales -Sterlite Optical Technologies is responsible for promotion of new products and applications for Sterlite’s range of Optical Fiber Solutions.

Salaj Sinha joined Sterlite in 1995 and his key focus area has been manufacturing, product development and projects.

Salaj Sinha holds a Bachelor Degree in Chemical Engineering from the Indian Institute of Technology (IIT-Kanpur).

About the Author