Optical beam direction compensating system for board-to-board free space optical interconnection in high-capacity ATM switch

Abstract

In interconnections between bookshelf-assembled asynchronous transfer mode (ATM) switch boards, a large number of micro-optical signal beams can be optically interconnected by a beam direction compensating system using a vertical cavity surface emitting laser, an x-y beam positioning sensor and a beam deflector made of an adjustable liquid prism. This beam direction compensating system can suppress the decrease in coupling efficiency between transmitters and receivers to no more than 15%, even if boards are inserted and extracted repeatedly, and are shocked repeatedly at a high intensity of 100 G. The compensation is very fast (20 ms). Furthermore, various optical interconnections necessary for ATM switching networks can be achieved by beam deflectors of a liquid crystal microprism array. In this preliminary study, we fabricate no more than eightchannel optical interconnections. However, since one surface emitting laser diode can have many channels in a small area (64 channels per 4 mm 2 ) and the aperture of this adjustable liquid prism is wide (28 mm in diameter) and uniform, a huge number of optical interconnection channels will be is possible using this system.Index Terms-ATM printed circuit boards, light deflectors, liquid crystal (LC), optical interconnections, switching systems.

Optical backplane with free-space optical interconnections using tunable beam deflectors and a mirror for bookshelf-assembled terabit per second class asynchronous transfer mode switch

“…4,13 This is because in the present system, optical beams are first aligned by tunable deflectors and then optical interconnections are fixed. 4,13 This is because in the present system, optical beams are first aligned by tunable deflectors and then optical interconnections are fixed.…”

“…4 If the speed of one channel is assumed to be 2.5 Gbit/s, the total throughput of this ATM switch will be 10 Tbit/s. The maximum possible number of optical channels on one board is 1000.…”

“…In a previous paper, 4 we reported autoactive alignment systems of optical interconnections between neighboring PCBs using 8ϫ8 micro-optic beam arrays ͑250-m pitch͒ for bookshelf-assembled PCBs for ATM switches. Switch large-scale integrated circuits ͑LSIs͒ are mounted on one PCB and are optically interconnected with a micro-optic beam direction compensation system, which suppresses optical beam fluctuations below Ϯ10 m. The coupling efficiency does not decrease even if the PCBs are inserted, extracted, and mechanically shocked with a high intensity of 100 G. This autoactive alignment system is inexpensive; it is used in commercially available handy video cameras.…”

Real-time validation of receiver state information in optical space–time block code systems

“…FSOIs are susceptible to diminished performance as a result of optical crosstalk from static and dynamic optical misalignment, beam expansion, turbulent atmospheres, and atmospheric scattering [4][5][6][7][8][9]. To mitigate the effect of optical crosstalk, various methods have been proposed including beam steering through microelectromechanical systems (MEMS), focusing through lensing systems, and multiple hardware links in a multiple-input multipleoutput (MIMO) configuration [10][11][12][13][14]. The carefully designed geometries of passive lensing system, and the reconfigurable geometries of MEMS are both means to optimize power transfer in the optical channel, but fail to correct dynamic thermal effects [8,9].…”

Robust free space board-to-board optical interconnect with closed loop MEMS tracking

“…Various strategies to adaptively compensate for the misalignment in free-space board-to-board optical interconnects have been demonstrated, including bulk optic Risley prisms [7,8], mechanical translational stages [9], liquid crystal spatial light modulators [10,11], and microelectromechanical systems (MEMS) devices [12,13]. Among these approaches, MEMS technology offers faster speed, low optical loss, and small form factor that can be directly integrated on top of VCSEL arrays [13].…”