Introduction

Intent

This method is intended to evaluate the adequacy of optical fibers and cables to retain their structural integrity and performance level under environmental conditions favorable for the development of fungal growth. These conditions are: high humidity, a warm atmosphere, and the presence of inorganic salts.

General effects

Organic materials commonly form an integral part of optical fiber: for plastic cladding, for protecting the surface of a glass fiber, and for buffering. Some fibers are fabricated entirely from various plastic materials. Organic materials are also commonly used in fabricating optical cable: bufferings, filling materials, strength members, and jacketing.

Micro-organisms digest certain organic materials as a normal metabolic process, thus degrading them and causing porosity and loss of structural integrity, even to the point of catastrophic failure. Basic resins do not usually serve as carbon sources for growth of fungi. Rather it is generally other components such as plasticizers, stabilizers, colorants, lubricants, and cellulosics that are responsible for the actual fungus attack.

Enzymes and organic acids produced during metabolism diffuse out of their cells and on to the plastic to cause such possible phenomena as cracking; corrosion; glass etching; hardening of cable filling compounds; increased modulus; weight changes; dimensional changes; and microbending of the fiber, with a resultant increase in attenuation.

Hazards

Because of safety and toxicity considerations detailed in 1.3.3, conduct testing at a site specifically equipped for the purpose. This generally means a separate, isolated facility with the ability to keep the test specimens within a confined area during the entire testing and incubation period.

Similarly, all testing shall be performed by personnel trained in microbiological laboratory techniques, sterile routines, and proper disposal of all waste solutions at the close of testing.

The reason for specifying the testing site and personnel qualifications is the potentially toxic nature of fungal spores. They have been implicated in pneumonia-like respiratory infections, ulcers of the skin, and digestive problems.