Telcordia GR-326 Standard for Fiber Optic Connectors

The Telcordia GR standard with universality and practicability has been widely used in global telecommunications industries. It has several specific categories designed for fiber optic connectors like Telcordia GR-326 standard for single mode optical connectors, Telcordia GR-1435 standard for multimode optical connectors, Telcordia GR-1081 standard for field-mountable optical fiber connectors, Telcordia GR-2923 for fiber optic connector cleaning products, etc. Among them, the Telcordia GR-326 standard that applied for single mode fiber connectors and jumper assemblies is the most commonly-used one. This article will uncover the mysterious veil of the Telcordia GR-326 standard.

Telcordia GR-326 Standard Backgrounds and Basics

The GR-326-CORE was initially created by Bellcore (Bell Communications Research, Inc.). In 1999, Bellcore officially renamed as Telcordia Technologies, and Telcordia was acquired by Ericsson in 2012. The Telcordia GR-326 ("Generic Requirements for Single-mode Optical Connectors and Jumper Assemblies") standard has kept being revised and improved during the time. A total of four issues of GR-326 have been released sequentially, and the current Issue 4 was put forward in February 2010. Issue 4 defines the latest requirements of connectors used for joining single mode optical fibers and for jumper assemblies made using such connectors.

The following basic information has presented to make a brief introduction of the GR-326 standard:

• Definition: Regarded as the most complete and rigorous standard for single mode fiber optic connectors. The Telcordia GR-326 standard document sets forth the Telcordia view of the technical generic requirements for, and characteristics required of, connectors used for joining single mode optical fibers, and for the jumper assemblies made using such connectors.

• Scope: Specifically for single mode field-terminated connectors and jumper assemblies.

• Target Audience: Intended for users or purchasers, and manufacturers, suppliers, or vendors of single mode fiber optic connectors and jumper assemblies.

• Categories: General Requirements; Performance Requirements; Service Life Testing; Extended Service Life Testing; Reliability Assurance Program.

Standard Telcordia GR-326 Connector Tests Introduction

A standard GR-362 Test covers two categories: Service Life Test & Extended Service Life Tests. The former is designed to simulate the stresses a connector may experience during its lifetime, which is divided into two sections—Environmental Tests and Mechanical Tests. And the latter will have exposure to a variety of environments, including additional Environmental Tests and Exposure Tests.

Service Life Test

The Environmental Tests are adopted to ensure the jumper assemblies will withstand the exposure to 85°C or temperature fluctuations of up to 125°C and accelerate the effects of aging on jumper assemblies, which include six parts:

Thermal Age Test

Content: simulate and accelerate the processes that may occur during shipping and storage of the product.

Requirements: Connectors are subjected to a temperature of 85℃ with uncontrolled humidity for a duration of 7 days.

Thermal Cycle Test

Content: make the temperature fluctuate over an expansive range—extreme heat and cold, apply heavy stress and strains to the sample to check whether it's qualified.

Requirements: Hanging the ambient temperature of the connector by 115℃ (75℃ to -40℃ ) over the course of three hours.

Humidity Aging Test

Content: Introduce moisture into the connector and to determine the effect that the moisture has on the samples.

Requirements: Setting the elevated temperature of 75℃ for 168 hours (7 days) while the connectors are exposed to 95% RH (relative humidity).

Humidity/Condensation Cycling Test

Content: To examine the effect that water has on the connector when a rapid transition in moisture occurs. If water molecules freeze or evaporate within the connector assemblies, then the issue of "gaps" in the physical contact between connectors within an adapter may expose.

Requirements: Temperature cycle from -10°C to + 65°C with 90%-100% RH for 168 hours (7 days) of 14 cycles.

Dry-out Step Test

Content: Prior to the last phase of the Environmental Tests. To remove any moisture that may remain from the previously performed Humidity/Condensation Cycling test.

Requirements: A drying step at 75℃ for 24 hours (1 day) before the Post-Condensation Thermal Cycle is performed.

Post Condensation Thermal Cycle Test

Content: Similar to the Thermal Cycle that was previously performed. The changes that may occur in the connector during Humidity/Condensation cycling are often revealed once the condensation is removed, and these changes can potentially affect the loss and/or reflectance of the connector.

Requirements: Conduct after the Dry-out step.

The mechanical tests will be required to be performed once the aging is complete, which include the following test items:

Vibration Test

Content: The connector assemblies are mounted in the "shaker," singly or in batches, in order to examine whether high frequencies of vibration will influence the performance of the samples.

Requirements: Conducted on three axis for two hours, and each axis is at an amplitude of 1.52mm with the frequency sweeping continuously from 10 and 55 Hz at a rate of 45 Hz per minute.

Flex Test

Content: Intended to simulate stresses on the terminated cable and the mated connector.

Requirements: Apply 0.9 kgf load, (may be reduced to 0.6 kgf load for Small Form Factor Connectors), then rotate the angle of the test fixture arm through the following cycle: 0°, 90°, 0°, -90°, 0°, and repeat for 100 cycles. Compare with the before and after numerical values of the loss and reflectance.

Twist Test

Content: A rotational strain will be put on the fiber, and the strength that is coupled with the connector will be tested. Like the flex test, the twist test will help to identify weaknesses in the termination process—the adequacy of the crimp.

Requirements: After mounting the test samples, apply load according to the instructions. Then rotate the capstan X revolutions about the axis of the fiber and reverse direction and rotate Y revolutions. Reverse direction again and rotate Y revolutions. After repeating the load applying procedure, nine times, the measure of loss and reflectance will get. Here is a table about the load and number of turns for twist tests.

Proof Test

Content: Ensures the strength of the latching mechanism of the connector, as well as the crimp during the termination process.

Requirements: Conducted through straight pull and 90° side pull tests to get the loss and reflectance measurement results.

TWAL (Transmission With Applied Load)

Content: Stress the samples by applying different weights at multiple angles. The series of weights used depends on the media type of the cordage, as well as the form factor.

Requirements: The tensile loads for transmission with the applied load is presented in the below table:

Impact Test

Content: Conducted to verify that the connectors are not damaged when they are dropped.

Requirements: A cinderblock is mounted to the bottom of the fixture, and the connector will be dropped from approximately 1.5 m from the horizontal planet. The connector contacts the cinderblock, and the process is repeated 8 times.

Durability Test

Content: Performed to simulate the repeated use of a connector to reveal the problems with the design or material flaws in the connector, such as any part of the latching mechanism that may be heavily strained or flawed by frequent use.

Requirements: Inserting the connector into an adapter repetitively (200 times) at different heights (in the sequence of 6ft., 4.5ft., 3ft., 3 ft., 4.5 ft., and 6ft.) so as to simulate what a user in the field might encounter when standing in front of a telecom rack.

Extended Service Life Test

The testing is non-sequential, so there is no cumulative effect. The Exposure Tests are covering the following testing items:

Dust Test

The dust has a great impact on optical performance. Particles that contaminate end-face will block optical signals and induce loss. This test involves intense exposure to dust of specified size particles in order to examine if there is a risk of any particle finding its way to the ferrule end-faces.

Salt Fog Test

The Salt Fog test is designed to guarantee the performance of the jumper assembly in free-breathing enclosures near the ocean, which involves exposing the connector to a high concentration of Sodium Chloride (NaCl) over an extended period. Optical testing is performed and followed by visual inspection to confirm that there is no evidence of corrosion on the materials.

Airborne Contaminants Test

The Airborne Contaminants test is designed to guarantee the performance and material stability of connectors in outdoor applications with high concentrations of pollution. The mated and unmated connectors will be exposed to various gases repeatedly to examine both optically and visually. An assortment of volatile gases is used in a small chamber for 20 days to simulate prolonged exposure to these elements.

Immersion/Corrosion Test

No optical requirements but involves a prolonged submersion in uncontaminated water instead. Mated connectors are checked for ferrule deformation by measuring the Radius of Curvature before and after the test, and comparing the values, while unmated connectors are checked for Fiber Dissolution, which involves checking to see if the fiber core has not recessed too far into the fiber cladding.

Groundwater Immersion Test

Intended to verify the ability of the product to withstand underground applications. During the test, the connector is exposed to a variety of chemicals found in sewage treatment and agricultural fertilization, among other applications, as well as biological mediums. These chemicals include ammonia, detergent, chlorine, and fuel.

Further Considerations

Some market analysts have predicted that the worldwide consumption volume of connectors will continue to grow steadily based on the previous average annual growth data. As demand for optical connectors increases globally, so does the supply. Although single mode fiber optic connector technology is relatively mature, there are changes being made to the optical performance that may impact how single mode fiber optic connectors are measured and tested.

The quality and reliability of fiber optic connectors and fiber optic cable assembly products must be taken into considerations. These components and procedures must be assured to meet the requirements of all pertinent industry specifications such as the internationally recognized GR-326 standards, and some other standards like ITU-T L.36 Standard. If you want your single mode fiber optic connectors and jumper assemblies will function well in telecommunications plant environments, selecting products with a Telcordia GR rating may ease your doubts.