| The 7/125 micron size may refer to the core (7) and cladding (125)
diameters of the fiber. This is not specific enough to determine
whether or not the fiber can be used. The parameter that is important is
the mode field diameter of the fiber. Mode field diameter is related to the
diameter of the core AND the index profile characteristics of the fiber.
Knowing the core diameter only does not provide sufficient information
to determine the MFD. This is an optical characteristic that of the fiber
that must be measured by the manufacturer.
Our specification for mode field diameter is:
8.2 to 10.5 microns
There are a few other characteristics that ought to be examined.
These are cutoff wavelength, zero dispersion wavelength, and dispersion
slope. The customer should be able to obtain these three parameter
values from the vendor who installed the fiber. If the parameter values
match our specifications, the next step would be to check (records or
re-test) the attenuation of the fiber.
The following information is excepted from our internal
specification for dispersion-unshifted single-mode fiber. It is
compatible with the SMF generally available from all SMF vendors (ATT,
Corning, for example).
Please let me know what your customers' exact fiber specifications
are. I'm interested is someone is selling SMF that falls outside our
specification limits.
Dick Kirk
NaC
FDDI Network Systems Engineering
From PS 17-10003-GS
3. REQUIREMENTS:
3.1 Mechanical
3.1.1. Optical Fibers: The optical fibers defined by this
specification shall be glass-on-glass fibers, as follows:
3.1.1.1. The fiber cladding shall be 125 +/- 2 microns diameter
glass, measured in accordance with EIA 455-45A, or -176.
3.1.1.2. The fiber shall be buffered to a minimum of 250 +/- 15
micron diameter measured in accordance with EIA 455-55 or -173. The
buffer shall be mechanically strippable. The buffer diameter shall be
specified in the detailed cable purchase specification.
3.1.1.3. The fiber cladding noncircularity shall be less than 2 % as
measured in accordance with EIA 455-45A or -176.
3.1.1.4. The fiber core to cladding concentricity error shall be
less than or equal to 1 micrometer measured in accordance with EIA
455-45A or -176.
3.1.1.5. The coating/cladding concentricity error shall be less than
or equal to 20 microns as measured in accordance with EIA 455-55 or -173.
3.1.1.6. The fiber shall be proof tested to a minimum of 0.35
GPascal (50,000 p.s.i) at an ambient room temperature of 23 +/- 2
degrees Celsius in accordance with EIA 455-31A.
3.2 Optical Requirements:
3.2.1 Attenuation
The fiber attenuation shall be such that cabled fiber attenuation
shall be less than 0.4 dB/Km at 1310 nm and less than 0.3 dB/km at 1550
nm as tested in accordance with EIA 455-78 (Cutback Method) over the
temperature range specified in the cable specification.
There shall be no localized attenuations greater than 0.1 dB.
Inspection shall be in accordance with EIA 455-59.
Page 3
3.2.2 Mode Field Diameter
The fiber shall exhibit a mode field diameter in the range of
8.7 to 10 � 0.5 micrometers as tested per EIA-455 -164, or -167.
3.2.3 Fiber Cutoff Wavelength
The fiber shall exhibit a cable cutoff wavelength less than or equal
to 1270 nm as tested per EIA 455 -170.
3.2.4 Chromatic Dispersion
The fiber shall exhibit a zero dispersion wavelength within the
range of 1300 to 1322 nm and a zero dispersion slope less than or equal
to 0.095 ps/(nm*nm*Km), as tested per EIA-455- 168, -169,or -175
3.2.5 Macrobending Loss
The fiber shall exhibit macrobending loss not to exceed 0.5 dB
at 1550 nm, using 100 turns on a 75 mm diameter mandrel. Testing to
be per EIA-455-62.
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Thank you for the information, it's very useful. However, I received
confirmation yesterday that the installed SMF is actually 8.2/125 micron,
therefore it complies with our requirements.
Thanks again for the information, I will use it in the future.
Later, have a nice holiday
Ray
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