Background: The conventional radio frequency (RF) paradigm does not scale to higher frequencies without great loss of channel capacity, increased bit error, increased noise factor, decreased amplifier gain, loss of the silicon CMOS platform and the VLSI which it represents and huge loss of form factor, in addition to the quasi-optical behavior of the RF field above about 150 GHz.
Mobile optical wireless technology directly addresses four key RF communications choke points:
1) Energy efficiency, or energy per bit, normalized to communication distance outside the rack.
2) Bandwidth efficiency, or the number bits carried by one symbol.
3) Channel efficiency, or the number of non-interfering optical channels that can be packed in one single-mode optical fiber.
4) Direct optical accessibility to the global network infrastructure.
Technology: Telecom wavelengths, general methodologies and new technology are extended to play a usher in the new paradigm of mobile optical wireless communication. Progress already made, principally in the electro-optical properties of silicon, epitaxial growth of germanium on silicon and in silicon micromachining is adapted to construct low power, integrated silicon electro-optical circuits to enable high data rate wireless optical communication between handheld or stationary user equipment and an all optical fronthaul network access to the Internet.
Along with mobile optical wireless technology it will be necessary to design integrated, compact, low power electrooptic liquid crystal polymer (LCP) structures for light steering and adaptive electrooptic lens structures for fine focus adjustments on the fly. The goal is to enable seamless optical connectivity between optical wireless user equipment and the Internet via "all-optical" downlink an uplink wireless interfaces with high data rate, low latency, and truly error free mobile communication compatible with Internet bit error rates.
It can be estimated that a silicon waveguide Mach-Zehnder modulator (MZM) can easily operate at 35GHz symbol rate. Four MZM modulators nested in quadrature configuration can produce 2 bits/ symbol, or 70Gb/s. If, in addition, two orthogonally polarized lights are each quadrature modulated, a total of 4 bits/symbol is obtained for one wavelength channel or 140Gb/s as a handheld uplink capacity/wavelength. More wavelength channels can be added in coarse wavelength multiplexing (CWM) as demonstrated by various labs using, for example, a silicon echelle grating. The downlink capacity will be limited by the germanium waveguide photodetector to about 35Gb/s.
Potential Commercial Applications:
Data center wireless links.
Optical wireless hotspot.
Secure wireless optical communication.
Mobile and stationary user equipment.
Extremely high single optical channel capacity; low power consumption; extremely low form factor, silicon CMOS technology and manufacturing ecosystem.
Direct use of existing Telecom network infrastructure through all optical fronthaul network.
***Note: white paper available upon request