s can be switched from one fiber to another. In 2D arrays, the mirrors can only flap up and down incorporating a single axis. 2D MEMS arrays will be used in smaller, 1G, all-optical switches because they are further along in the development process. As MEMS is based on mechanical movement, it offers the best isolation performance available. For the same reason, MEMS cannot be used for drop-and- continue applications. Optics Primer Table 2-11 Thermo- Acousto- Holo- Characteristics of Bubbles optics optics grams Switching Tech- nologies Scalability Very high Medium Medium Medium Medium Switching Medium Medium Medium Medium speed Reliability Moving parts 2.5-6 dB, 32X32: up to 2.5 dB 16x16: 32X32 Power Medium Very low Unknown Very high Unknown Medium, consumption when based on silica requires voltages In LXT, light is passed through liquid crystals that alter their transmis- sion characteristics when an electric current is applied. Most LXT devices depend on the polarization properties of the light for switching. LXT offers particularly low power consumption. LXT devices can throttle the amount of light that passes through them. They can therefore be used as variable attenuators or power splitters with a configurable splitting ratio. The latter enables various drop-and-continue applications. LXT switches have good scalability; however, the technology will first be used for modestly sized, wavelength-selective devices. LXT can be combined with electroholographic technology for increasing switching speeds. As discussed previously, bubbles formed by printer ink pens have sur- faces that act like mirrors. Bubbles are currently used for optical switches by reusing parts of the Desk Jet printer technology. The technology is intended for use in add/drop multiplexers (ADMs) and scalable switches. Thermo-optics consists of passive splitters. When these are heated, their refractive index is changed to alter the way in which they divide wave- lengths between either of the two output ports. They are wavelength sensi- tive and n