**3. Conclusion**

160 Optical Communications Systems

In Fig. 15, an external view of "The least stand-by power system using a 1x7 optically-gated optical switch" currently being developed is shown. The specifications of both the OLT (Optical Line Terminal) and the ONU (Optical Network Unit) are summarized in Table 2

Fig. 15. External view of "The least stand-by power system using a 1x7 all-optical switch".

Electrical Interface OLT Tx+/- 1250Mbps DATA\_IN LVPECL SMA NRZ

Electrical Interface OLT RX+/- 1250Mbps DATA\_OUT LVPECL SMA NRZ

Controll Item LD ON/OFF LOS Monitor

Output Power ≧+3.5dBm@Enable≦-39dBm@Disable

LOS Detection ≧-45.0dBm(Detection)≦-30.0dBm(Release)

Wavelength 1310-1490 nm

Wavelength 1310-1490 nm Min. Input Power ≦-30.0dBm Max. Input Power ≧-8.0dBm

Extinction Ratio ≧9dB

Display LED Power Supply, LD, LOS Switch SW Power Supply, LD

Controll Interface USB Rev. 2.0 full speed USB-B

Size - W210mm × D350mm × H99mm

Table 2. Specifications of OLT (Optical Line Terminal) Optical Interface Unit.

Lock Key LD Source

Power Supply - DC 5V, 0.8 W

Weight - 2.5 kg

and Table 3, respectively.

E/O Unit

O/E Unit

Function

Others

Optical Interface

Optical Interface

A versatile optically gated optical switch using an organic dye is suitable for light-path switching in optical communication at various wavelengths of the signal light. The feature of utilizing a thermal-lens effect generated in a thin layer of a dye solution is possible to cover a wide range of wavelengths by varying the types of pigment. An organic dye for absorbing the gating light combined with a high-boiling solvent for forming a thermal lens is properly selected by choosing the wavelengths of both the gating light and the signal light. The formed thermal-lens in a dye solution is very small, which brings about highspeed switch of around 1 msec.

An epoch-making 1x7 optically-gated optical switch has been developed using both a 7 bundled optical fibre with a centre-core distance of 40 μm and a prism of a hexagonal truncated pyramid. Around 0.6 of the coupling efficiency of incidence light to a 7-bundled optical fibre and smaller than 40 dB of crosstalk for both incidence light have been achieved. Using the 1x7 optically-gated optical switch, we have developed a least stand-by power system as well. This system is located in a home, and is composed of the 1x7 optically gated optical switch and a reflection-type optical star coupler, which directly connects between an optical coupler from a telephone office and a PC, TV, IP-phone, etc. Using this system, the least stand-by power in the home will be achieved.

**Part 3** 

**Optical Communications Systems:** 

**Multiplexing and Demultiplexing** 
