The purpose of this test procedure is to determine the loss in fiber optic interconnection devices intended for single and multichannel or hybrid configurations@ or both. It establishes the insertion loss as would be experienced in several usage conditions and may be used for quality assessment purposes. The procedure is to take measurements from which insertion loss (decrease in useful power) can be calculated. The methods used in this procedure are designed to provide the insertion loss as would be experienced at the anticipated extremes of system applications@ both short and long length links. This test will establish insertion loss for: Method A: Short lengths in which steady state modal conditions do not exist at the interconnection. Method B: Long lengths in which steady state modal conditions exist at the interconnection. Method C: User Specified Conditions.