The fiber is cut at internal end (see last 2 photos). Spool length is tested in our lab as shown in last photo below.

See specification at page 20 of the 2nd pdf link below.

Dispersion Shifted Single-mode Fibers Optical Specifications
Corning SMF/DS CPC3 (Issued: 7/92)
Attenuation @ 1300nm (dB/km) <= 0.5 (typical)
Attenuation @ 1550nm (dB/km) <= 0.25
Attenuation vs Wavelength: 1525-1575nm Max difference 0.05 db/km (ref. 1550nm)
Mode Field Diameter @1550nm 8.1 +/- 0.65 um
Typical Core Diameter 8.2 um
Zero Dispersion Wavelength 1535nm <= WL0<= 1565nm
Zero Dispersion Slope S0 <= 0.085 ps/km*nm2
Total Dispersion (ps/nm*km) <= 2.7 over the range 1525 to 1575nm
PMD Link Value <= 0.1 ps/km
Dispersion Calculation:
D(WL) = S0*(WL – WL0)[ps/nm*km], for 1500nm <= WL <= 1600nm

Dispersion-shifted fiber (DSF), specified in ITU-T G.653, is a type of single-mode optical fiber with a core-clad index profile tailored to shift the zero-dispersion wavelength from the natural 1300 nm in silica-glass fibers to the minimum-loss window at 1550 nm. The group-velocity or intramodal dispersion which dominates in single-mode fibers is comprised of both material and waveguide dispersion. Waveguide dispersion can be made more negative by changing the index profile and thus be used to offset the fixed material dispersion, shifting or flattening the overall intramodal dispersion. This is advantageous because it allows a communication system to possess both low dispersion and low attenuation. However, when used in wavelength division multiplexing systems, dispersion-shifted fibers can suffer from four-wave mixing which causes intermodulation of the independent signals. As a result nonzero dispersion shifted fiber is often used.

DSF: To minimize chromatic dispersion at 1550 nm, a new fiber called dispersion-shifted fiber (DSF) was introduced in the early 1980's. By changing the index profile and reducing the core radius, fiber designers were able to move WL0 from the 1310 nm window to the 1540 to 1560 nm window. Though effective in greatly reducing chromatic dispersion effects, which limits bandwidth, the positioning of WL0 in close proximity to the operating wavelengths resulted in a tendency to a nonlinear distortion effect called four wave mixing (FWM). This is especially troublesome in DWDM applications with more than eight wavelengths. Typical losses range from 0.25 to 0.30 dB/km.

Note: Zero dispersion wavelength of standard DSF fiber is 1557.5 ±12.5 nm (i.e. 1544.5 nm to 1569.5 nm).

It is ITU G.653 fiber, see ITU G.653 fiber info at last pdf link below.