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Providing power from the central office to telephone apparatus is used in copper-based systems to achieve high availability, low cost, and low electricity power consumption. It is feasible to power the telephone at customer premises optically by sending optical power over the optical fiber connection. Very-low-power-consumption optical communications systems such as interferometer-based systems must be used. The power consumption of a standard telephone apparatus in its different states is analyzed, and a simple mathematical model is developed and used to calculate the power required to operate the telephone for different durations of different states. Optical power levels transmitted over optical fiber are limited by nonlinear effects and safety standards. The mathematical model is used to compare the power consumption, electricity cost, and carbon footprint of a telephone system over copper twisted pair, GPON, and interferometric systems. Current standard GPON and EPON equipment cannot be powered over optical fiber, and must use battery backup. An interferometric system can consume less power than a copper-based system, depending on the optical source's electrical-to-optical conversion efficiency, the photovoltaic cells' optical to electrical conversion efficiency, and Call and Ringing durations. Low-cost telephone service with 24/7 availability over optical fiber provides the infrastructure to offer broadband and HDTV exploiting the more than 30,000 GHz capacity of the optical fiber.