When light passes through a passive optical component, the optical power decreases. This decrease is called an insertion loss.

The statement provides an accurate and fundamental definition of insertion loss in the context of optical fiber communications. Insertion loss is the measure of the reduction in optical power that occurs when a passive device, such as a connector, splice, or splitter, is inserted into the path of a light signal. This loss is an unavoidable characteristic of all passive components due to physical phenomena like absorption, scattering, and reflection at material interfaces. It is a critical parameter for calculating the total attenuation (power budget) of an optical link to ensure the signal at the receiver is above the required sensitivity threshold.

This is a "TRUE OR FALSE" question. The alternative, "False," is incorrect because the statement is a standard, technically correct definition used in optical network engineering and design. There is no ambiguity; the described phenomenon is precisely what is termed "insertion loss."

1. Huawei HCIA-Access V2.5 Training Material. In the module covering Optical Distribution Network (ODN) fundamentals, insertion loss is defined as the power loss introduced by components in the optical path. The material emphasizes that the cumulative insertion loss of all components (splitters, connectors, splices) must be calculated to ensure the link's power budget is met. (Refer to: HCIA-Access V2.5 Training Material, Chapter 4: ODN Network Planning and Design).

2. International Telecommunication Union (ITU-T) Recommendation G.671. This standard, which specifies the transmission characteristics of optical components, formally defines insertion loss. It states: "The insertion loss of an optical component is the ratio, expressed in dB, of the optical power P1 launched at the input port of the component to the optical power P2 from the output port, when the component is inserted between the launching and receiving system." (Source: ITU-T Recommendation G.671, "Transmission characteristics of optical components and subsystems," Section 3.1.1: Definitions - Insertion Loss).

3. University Courseware on Optical Communications. Reputable academic programs consistently define insertion loss in this manner. For instance, lecture materials on fiber-optic systems explain that any component added to a fiber link will introduce a loss, quantified as insertion loss, which is calculated as -10 log10(Pout / Pin), where Pout is the output power and Pin is the input power. (Source: MIT OpenCourseWare, 6.453 Quantum Optical Communication, Lecture Notes on Optical Fiber and Components).