14.1.1 Use Case 1: Represent an Optical Fiber Installation

The Optical Path data object has been designed to address the following scenarios:

• Installation of an optical path that consists of multiple fiber segments joined via splices, connections and turnarounds. Optical fibers can adopt multiple configurations such as:

• Straight fiber with a termination at the end.
• ‘J’ configuration.
• Dual-ended fiber that terminates back in the instrument box.

For diagrams of these and other geometries, see Figure 16.3-1 .

Optical fiber installation is not restricted to wells. The data schema has been designed to accommodate other deployment scenarios where optical fiber could also be applied, such as pipelines.

Further note that the optical fiber installations are used in a similar manner for distributed acoustic and strain sensing (DAS and DSS) applications. For DAS PRODML (Part V. Distributed Acoustic Sensing) the same definition of installation of optical paths apply,

The data schema is extremely detailed, allowing great flexibility and fine granularity at the same time. It is possible easily to document things such as:

• Location of splices, and their type.
• Signal loss and reflectivity properties on a per-fiber-segment basis.
• Overstuffing (whereby the length of fiber is greater than that of the physical facility being measured).
• Type of material used in the optical fiber.
• Conveyance of the fiber, e.g. in a control line, in a permanent cable, deployed in a wireline logging mode, etc.
• Map the length along the optical path to specific facility lengths, so that the analyst knows which parts of a measurement pertain to the wellbore, pipeline etc. which they are analyzing.
• Denote locations in the fiber where fiber defects exist so that future troubleshooting of the measurements can take into account the presence of these defects.
• Store calibrations of the Instrument Box or whole system.
• Store OTDR (Optical Time Domain Reflectometry) a type of diagnostic test on the optical path) information, including the type of equipment and personnel used for taking the OTDR.
• Represent the DTS Instrumentation Box that has been installed, either permanently connected or as a temporary installation, to the optical fiber. Several details regarding the instrumentation can be represented through the data schema, ranging from make/model of the box, contact information on the person who installed it, configuration data, and calibration data, to diagnostics information. The DTS Instrument Box is sometimes known as a “Lightbox”.
• Represent DTS Installation comprising one Optical Path and one Instrument Box. This is the “unit” which generates measurements. Various configurations can be represented this way, such as an Instrument Box that will be shared among multiple optical fibers in one or multiple physical locations (a “drive-by” instrument box).