Fiber and Probe Installation Guidelines

• Guided Wave recommends that the optical fiber run through a cable tray or a conduit. This provides both mechanical and environmental protection for the fiber.
• A suitable watertight flexible conduit may be used to connect the probe to the rigid conduit. Enough slack must be left in the flexible conduit to allow for the motion of the probe during referencing, cleaning, or removal from the process line.
• If the fiber is run unprotected a protective sleeve or coupling must be installed on the probe to protect the SMA/bulkhead connector from the elements.
• All junction boxes that will hold extra fiber (standard 500″m core diameter) must be at least 30cm (12 inches) across. FIBER SHOULD NOT BE SUBJECTED TO A BEND RADIUS OF LESS THAN 15cm (6 INCHES). However, a smaller radius may be acceptable for fiber with a smaller core diameter.
• Probes require periodic service and the fiber optic cable must allow enough of a service loop to allow servicing without removal of the cable from the probe.
• Fiber optic cable runs should be sized so that you have 1 to 2 meters extra on each end to allow for service. Store the extra fiber in junction boxes.
• When not in use, fiber connectors must be covered by the small dust caps provided. Do not remove these caps until the fiber is installed.
• Fiber conduit must be sized so that it will provide adequate clearance to pull terminated cables.
• The fiber optic cables are an integral part of the spectrometer. The terminations must be rigorously inspected. Any flaws will degrade system performance. Thus, Guided Wave recommends that you purchase your fiber pre-terminated.

Free Standing Cables

Cables attached along building walls, or piping should be secured every 1 to 2 meters (3 to 6 feet) for both vertical and/or horizontal installations. The cable should be buffered from cable ties by a soft elastomer grommet or laid through an 8 to 10 mm (0.3 to 0.4 inch) diameter, 50 to 75 mm (2 to 3 inch) long, split soft tube. A cable drop of 15 to 20 cm (6 to 8 inch) per 1 to 2 meters (3 to 6 feet) horizontal support provides the best buffering. For aerial installations, a guide wire should be used for support.

Note

The cable is capable of supporting itself over 100 meters (330 feet) or more, but it will be overly sensitive to environmental effects. Attachment to the guide wire is the same as free standing cables except a soft adhesive (e.g. RTV silicone) should be used to prevent the drop of the cable from shifting between tie points.

Cable Relaxation

Once the cable is installed, it should be checked for sharp bends, loops, or crimping. If the installation is done properly, the cable will then require time to relax. At a 25 °C (77 °F) ambient, this will require 1 to 2 days; however, if the ambient temperature is colder, more time will be required.

Environmental Effects

The environment influences performance. Low temperature can affect throughput of the cable, particularly below –60 °C (-76 °F) where a phase change of  the buffer material occurs.

Thin layering of ice (aerial installation) has a slight effect on the throughput while freezing water in underground ducts can cause permanent damage.

Hydrogen rich environments cause optical detail to be generated in the NIR spectral range. The hydrogen gas permeates the glass filament and causes detailed spectral bands to appear. This phenomenon appears to be only cause by hydrogen.

Vibration

Vibration does not affect the fiber optic cable unless the cable is in tension or longitudinal compression. If such conditions cannot be avoided, then shield the cable from contact with surfaces subject to severe vibration.

Understanding Jacketed Fiber Optic Cable

Guided Wave’s jacketed single strand fiber optic cable has unique handling requirements. These requirements reflect the unique nature of a glass filament. Specifically, a glass filament has very high tensile strength but very low shear strength.

As a wave guide, the walls of the filament become sensitive to applied pressure resulting in localized attenuation over broad spectral ranges or selected narrow spectral ranges depending on the periodicity of the pressure along the fiber axis.

The fiber optic cable is constructed of a glass fiber with a soft resilient material adjacent to the wave guide, followed by harder materials. Longitudinal tensile members are also added to off load tensile forces from the glass fiber.