Common use of Electro Optic Switches Clause in Contracts

Electro Optic Switches. One example of Electro Optic Switches is Lithium Niobate (LN) based switches, operating using electro-optic (EO) effect whereby applied electrical field changes the refractive index of LN. Products are available such as marketed by EO SPACE. EO effect is very fast but weak in LN, hence typically the switch chip is large (waveguide length in the order of several cm is needed to achieve the π phase shift needed). Other materials can provide significantly higher EO effect with speeds sufficient for switching purposes. An example is lead lanthanum zirconate titanate (PLZT) based switches as marketed by EpiPhotonics (see Figure 12). These can provide a speed of < 10ns and a number of configurations are available from 1×N (N=1-16) and N×N (N=2-4, with N=8 under development). EO switches are power efficient as they only require electrical voltage (field) to hold their state, with no current. Energy is only consumed when switching takes place and current is needed to charge the capacitance. Yet technologies based on transparent waveguide materials have a common drawback. As they are generally based on optical phase changes and interference in transparent waveguides, they cannot realise very high extinction ratio (ER) (i.e., cannot switch ‘off’ light signals sufficiently) hence will have scalability issues due to crosstalk. For example, the PLZT switches by Epiphotonics have about 30dB crosstalk level when they are small-scaled, but when scaled up to N≥8, this drops to 18 dB, a level that may not be acceptable by systems engineers. NTT have published data on similar product technology. Another issue with these technologies is that as passive components, all MEMS, mechanical and thermal switches have insertion loss hence cannot realize lossless switching. Again as an example the PLZT switches have 5dB insertion loss at small scale, increasing to 7.5 dB when scaled up to 4×4. Figure 12: PLZT 1xN switch

Electro Optic Switches. One example of Electro Optic Switches is Lithium Niobate (LN) based switches, operating using electro-optic (EO) effect whereby applied electrical field changes the refractive index of LN. Products are available such as marketed by EO SPACE. EO effect is very fast but weak in LN, hence typically the switch chip is large (waveguide length in the order of several cm is needed to achieve the π phase shift needed). Other materials can provide significantly higher EO effect with speeds sufficient for switching purposes. An example is lead lanthanum zirconate titanate (PLZT) based switches as marketed by EpiPhotonics (see Figure 1211). These can provide a speed of < 10ns and a number of configurations are available from 1×N (N=1-16) and N×N (N=2-4, with N=8 under development). EO switches are power efficient as they only require electrical voltage (field) to hold their state, with no current. Energy is only consumed when switching takes place and current is needed to charge the capacitance. Yet technologies based on transparent waveguide materials have a common drawback. As they are generally based on optical phase changes and interference in transparent waveguides, they cannot realise very high extinction ratio (ER) (i.e., cannot switch ‘off’ light signals sufficiently) hence will have scalability issues due to crosstalk. For example, the PLZT switches by Epiphotonics have about 30dB crosstalk level when they are small-scaled, but when scaled up to N≥8, this drops to 18 dB, a level that may not be acceptable by systems engineers. NTT have published data on similar product technology. Another issue with these technologies is that as passive components, all MEMS, mechanical and thermal switches have insertion loss hence cannot realize lossless switching. Again as an example the PLZT switches have 5dB insertion loss at small scale, increasing to 7.5 dB when scaled up to 4×4. Figure 12: 11 PLZT 1xN switch