User Manual

Measuring Chromatic Dispersion: Theory
92 FTB-5800
Using Data Fits to Obtain Dispersion
Using Data Fits to Obtain Dispersion
This section gives you details about the way EXFO uses the data fits to
obtain dispersion. Once group delays are computed, equations are fitted in
order to obtain dispersion, dispersion slope and zero-dispersion
wavelengths. The dispersion curve of typical singlemode fibers follows
certain equations used to interpolate zero-dispersion wavelength and
slope. The following table graph shows the equations applied to
singlemode fibers in specific wavelength ranges.
Fiber Type
and Wavelength Range
Expression for D
Standard SM
Dispersion-shifted
1500 nm-1600 nm
Non-zero dispersion-shifted
up to 1560 nm
Non-zero dispersion-shifted
1530 nm-1565 nm (C Band)
1565 nm-1625 nm (L Band)
Dispersion-shifted
1200 nm λ 1600 nm≤≤
τλ() ABλ
2
Cλ
2–
++=
D λ() 2Bλ Cλ
3–
–()=
τλ() ABλ
2
Cλ++=
D λ() 2Bλ C+=
D λ()
D1560()D 1530()–
30
-------------------------------------------------
°
λ 1560–()⋅
⎩⎭
⎨⎬
⎧⎫
D 1560()+=
D λ()
D1565()D 1530()–
35
-------------------------------------------------
°
λ 1565–()⋅
⎩⎭
⎨⎬
⎧⎫
D1565()+=
D λ()
D 1625()D 1565()–
60
-------------------------------------------------
°
λ 1625–()⋅
⎩⎭
⎨⎬
⎧⎫
D 1625()+=
1200 nm λ 1600 nm≤≤
τλ() ABλ Cλλ()ln++=
D λ() BCC λ()ln++=