Optical Time-domain Reflectometer - Types of OTDR-like Test Equipment

Types of OTDR-like Test Equipment

The common types of OTDR-like test equipment are:

• Full-feature OTDR
• Hand-held OTDR
• Fiber Break Locator
• RTU in RFTSs

The equipment is summarized below, and detailed in GR-196, Generic Requirements for Optical Time Domain Reflectometer (OTDR) Type Equipment.

• Full-feature OTDR

  Full-feature OTDRs are traditional, optical time domain reflectometers. They are feature-rich and usually larger, heavier, and less portable than either the hand-held OTDR or the fiber break locator. Despite being characterized as large, their size and weight is only a fraction of that of early generation OTDRs. Often a full-feature OTDR has a main frame that can be fitted with multi-functioned plug-in units to perform many different fiber measurement tasks. Larger, color displays are common. The full-feature OTDR often has a greater measurement range than the other types of OTDR-like equipment. Often it is used in laboratories and in the field for difficult fiber measurements. Most full-feature OTDRs are powered from an AC source and or battery source.

• Hand-held OTDR and Fiber break locator

  Hand-held (formerly mini) OTDRs and fiber break locators are designed to troubleshoot fiber networks in a field-type environment often using battery power. The two types of instruments cover the spectrum of approaches to fiber optic plant taken by the communications providers. Hand-held, inexpensive (compared to full-feature) OTDRs are intended to be easy-to-use, light-weight, sophisticated OTDRs to collect field data and perform rudimentary data analysis upon. They may be less feature rich than full-feature OTDRs. Often they can be used in conjunction with PC-based software to perform easy data collection with the hand-held OTDR and sophisticated data analysis with the PC-based software. The hand-held OTDRs are commonly used to measure fiber links and locate fiber breaks, points of high loss, points of high reflectance, link end-to-end loss, and Optical Return Loss (ORL) for the link.

  Fiber break locators are intended to be low-cost instruments specifically designed to locate the position of a catastrophic fiber event, e.g., fiber break, point of high reflectance, or high loss. The fiber break locator is an opto-electronic tape measure that is designed to measure only distance to catastrophic fiber events.

  In general, hand-held OTDRs and fiber break locators are lighter and smaller, simpler to operate, and more likely to operate using battery power than full-feature OTDRs. The intent is for hand-held OTDRs and fiber break locators to be inexpensive enough for optical technicians to be equipped with one as part of their standard tool kit.

• Remote Test Unit (RTU)

  The RTU is the testing module of the RFTS described in GR-1295, Generic Requirements for Remote Fiber Testing Systems (RFTSS). An RFTS enables fiber physical plant to be automatically tested from a central location. A central computer is used to control the operation of OTDR-like test components located at key points in the fiber network. These test components will scan the fiber to locate problems. If a problem is found, its location is noted and the appropriate Operations Systems (OSs) are notified to begin the repair process. The RFTS can also provide direct access to a corporate database that contains a historical repository for the OTDR fiber traces and any other fiber records for the physical fiber plant.

  Since OTDRs and OTDR-like equipment have many uses in the communications industry, their possible operating environment is varied, ranging from indoors to outdoors. Most often, however, these test sets are operated in controlled environments, accessing the fibers at their termination points on fiber distributing frames. Indoor environments include controlled environments such as in central offices (COs), equipment huts, or Controlled Environment Vaults (CEVs). Use in outside environments is rarer, but may include use in a manhole, aerial platform, open trench, or a splicing van.