A scalable and switchless optical network structure, employing a single 32x32 free-space grating multiplexer

Use of a single N x N wavelength multiplexer, to interconnect optically of order N-2 terminals without the use of space switches (hence switchless), is limited by call blocking and crosstalk in the multiplexer, Since all ports re-use the same wavelengths, poor crosstalk can cause severe homodyne beatnoise, particularly in planar N x N multiplexers; A scalable, distributed, optical broadcast-switching network structure has been demonstrated, which overcomes blocking by using wavelength conversion in ''dummy'' ports around a 32 x 32-port free-space grating multiplexer, Measured background crosstalk rejection below -60 dB would allow 170 x 170 ports with tolerable beat-noise, supporting 7300 terminals (without concentration or time-sharing), With further expected crosstalk improvements, free-space N x N multiplexers are essential for scaling the architecture to large networks, which could interconnect up to millions of terminals (with concentration or time-sharing).