■Infrared vs Other Communication Method

	Signal		Media
Cable	electrical signal		copper cable
	optical signal		optical fiber cable
Wireless	electromagnetic wave	radio (≦3THz)	air (license)
		infrared beam	air (no constraints)

• Infrared is free from radio wave law.
• This area is free and self-responsible.

■Radio Wage vs Optical Beam

Description	Radio Wave	Optical Beam
Mobile	◎	×
Low cost	○	△
Strong for interception	◎	×
Cross talk	×	○
Broadband and high speed	△	◎
Directivity and security	△	◎
Immunity for electric noise	△	◎