Design of an Optical Wireless Transmission Link Student Name: Wen Zu Instructor: Dr.Xavier N. Fernando

Content: Selection of wavelength Selection of wavelength System Structure System Structure Alignment and tracking, Adjustment Alignment and tracking, Adjustment and Calculation Assumptions and Calculation Problems in the next step Problems in the next step References References

1. Selection of wavelength:1550nm Options of wavelength:780 nm to ~ 850nm, 1300nm~1550nm and 9 micron. Options of wavelength:780 nm to ~ 850nm, 1300nm~1550nm and 9 micron. Advantages of using 1550nm: Advantages of using 1550nm: 1.50 times more transmitted power at 1550 nm than 800 nm considering the eye safety limit. The eye safety limit of 1550 nm is 100 mW/cm ², comparing to 20 mW/cm 2.Receivers have nearly 3 dB better receiver sensitivity at 1550nm than 850nm due to the lower energy per photon.

nm is the most commonly specified wavelength range for fiber-based optical communication. The supporting technical base for this wavelength range is vast and growing rapidly every year. Therefore, it will be easy to access new cost-effective technologies to update this design, and to keep this design on the top performance nm is the most commonly specified wavelength range for fiber-based optical communication. The supporting technical base for this wavelength range is vast and growing rapidly every year. Therefore, it will be easy to access new cost-effective technologies to update this design, and to keep this design on the top performance.

2. Structure A five – beam system. Four beam are used to transmit down. One beam is used to transmit up, and used in Alignment and tracking, Adjustment systems. A five – beam system. Four beam are used to transmit down. One beam is used to transmit up, and used in Alignment and tracking, Adjustment systems.

Figure 1. The function parts of this design

Figure 2. The function parts of this design(2)

Figure 3.The working of transmitters and receivers.

3. Alignment and tracking, Adjustment Alignment and tracking system is designed to co- align the transmit and receive optical axes when settle these devices, and to keep the alignment of transmitters and receivers in the future. Buildings could bend, vibrate, or move slightly in wind or uneven thermal loading, e.g. sunshine on one side. This system receives dictations from a micro processor system, and operate a 2D mechanical structure- servo system. Figure 5,6 show tracking system ’ s use in CANON Optical Wireless Communication designs. Alignment and tracking system is designed to co- align the transmit and receive optical axes when settle these devices, and to keep the alignment of transmitters and receivers in the future. Buildings could bend, vibrate, or move slightly in wind or uneven thermal loading, e.g. sunshine on one side. This system receives dictations from a micro processor system, and operate a 2D mechanical structure- servo system. Figure 5,6 show tracking system ’ s use in CANON Optical Wireless Communication designs.

Figure 5. Auto-Tracking System Figure 6. Effect of Beam Diameter on Receiver Figure 6. Effect of Beam Diameter on Receiver

Adjustment system operates transmit optics to fulfill the function showing in figure 3 depending on the real BER in different weathers, and to maintain an acceptable system performance.Adjustment system operates transmit optics to fulfill the function showing in figure 3 depending on the real BER in different weathers, and to maintain an acceptable system performance.

4. and Calculation 4. Assumptions and Calculation : Assumptions: Transmitter: Laser (1550nm) x 5 Transmitter: Laser (1550nm) x 5 Average Laser Power: 1000mw/30dBm Average Laser Power: 1000mw/30dBm Transmit Divergence: 0.5 mrad(1/e^2 ) Transmit Divergence: 0.5 mrad(1/e^2 ) Transmit aperture: 4cm Transmit aperture: 4cm Receiver: InGaAs APD (1550nm) x 5 Receiver: InGaAs APD (1550nm) x 5 Receiver Sensitivity: -37 dBm Receiver Sensitivity: -37 dBm Receive Aperture: 15cm Receive Aperture: 15cm Max. Data Rate: 1000Mbps x 4 Max. Data Rate: 1000Mbps x 4

Maximum Range at -220dB/km atmosphere attenuation Maximum Range at -220dB/km atmosphere attenuation Figure 3 shows the main atmosphere attenuation - Mie scattering, varies with wavelengths. The max. atmosphere 1550nm is -220dB/km, and atmospheric loss is 62dB: Max. Range = 281m. Max. Range = 281m.

BER: 1.00E-12 BER: 1.00E-12 Transmit Optics Degradation: -1dB Transmit Optics Degradation: -1dB Receive Optics Attenuation: -1dB Receive Optics Attenuation: -1dB Calculation Calculation Eye safety Eye safety Transmit power/Transmit area =79.6mw/cm ² < 100 mW/cm ² (Eye safety Transmit power/Transmit area =79.6mw/cm ² < 100 mW/cm ² (Eye safety Beam < Receive Aperture: 15cm Beam < Receive Aperture: 15cm Max. link power margin= Transmit Power x 4 (36dBm)-Receiver Sensitivit (-30dBm)- Geometric Range Loss(1)-Transmit Optics Degradation(1)-Receive Optics Attenuation(1)-Filter Loss(1)= 62dB Max. link power margin= Transmit Power x 4 (36dBm)-Receiver Sensitivit (-30dBm)- Geometric Range Loss(1)-Transmit Optics Degradation(1)-Receive Optics Attenuation(1)-Filter Loss(1)= 62dB

Figure 4. Mie scattering attenuation in dB/km for the various fog distribution models

5.Problems in the next step Design of transmit optic and receive optic. Design of transmit optic and receive optic. Completing design of alignment and tracking system Completing design of alignment and tracking system Completing design of adjustment system Completing design of adjustment system

References: Z.Ghassemlooy, “Optical Wireless Communications - Our Contribution” Z.Ghassemlooy, “Optical Wireless Communications - Our Contribution” J.R. Barry, “ Wireless Infrared Communication ”, Kluwer Academic Press, Boston, 1994, 1st edn. Chaturi Singh, Y.N.Singh, J.John, K.K.Tripathi, “High-Speed Power-Efficient Optical Wireless System” Scott Bloom, Seth Hartley, “THE LAST-MILE SOLUTION : HYBRID FSO RADIO” Scott Bloom, Seth Hartley, “THE LAST-MILE SOLUTION : HYBRID FSO RADIO” Scott Bloom,” THE PHYSICS OF FREE-SPACE OPTICS” Scott Bloom,” THE PHYSICS OF FREE-SPACE OPTICS” Isaac I. Kim, Eric Korevaar,” Availability of Free Space Optics (FSO) and hybrid FSO/RF systems” Isaac I. Kim, Eric Korevaar,” Availability of Free Space Optics (FSO) and hybrid FSO/RF systems” Jim Alwan, “EYE SAFETY AND WIRELESS OPTICAL NETWORKS” Jim Alwan, “EYE SAFETY AND WIRELESS OPTICAL NETWORKS” fSONA Communications Corp. ‘WAVELENGTH SELECTION FOROPTICAL WIRELESS COMMUNICATIONS SYSTEMS” fSONA Communications Corp. ‘WAVELENGTH SELECTION FOROPTICAL WIRELESS COMMUNICATIONS SYSTEMS”