Optical basics

Optical Terminology

SM	- Single Mode fiber.
MM	- Multi Mode fiber.
WDM	- Wave length Division Multiplexing.
DWDM	- Dense Wavelength Division Multiplexing.
CWDM	- Coarse Wavelength Division Multiplexing.
OADM	- Optical Add Drop Multiplexers.
EDFA	- Erbium Doped Fiber Amplifier.
GBIC	- Giga Bit Interface Converter.
SFP	- Small Form-factor Pluggable).
O-E-O	- Optical-Electrical-Optical.
FC	- Fiber Channel.
OSNR	- Optical Signal to Noise Ratio

Optical fiber - 3 components, Core, Cladding, Coating



Fiber types - MM (Multi Mode), SM (Single Mode) (Generally SM is yellow color cable and MM is orange color cable)



Data is sent as light pulses through the optical cable.

Conventional optical networks wave lengths - 850nm, 1310nm, 1550nm.
Light source

• 850nm uses LED (Cheap, short distance)
• 1310nm uses LED or laser (Cheap, medium distance)
• 1550nm uses High quality laser(Expensive .

WDM - Wavelength Division Multiplexing.

DWDM - Dense Wavelength Division Multiplexing
In DWDM space between channels(wavelengths) is less, so needs good light source to send good signal.
DWDM uses expensive powerful lasers.
DWDM is used for long distance transmissions.

CWDM - Coarse Wavelength Division Multiplexing
In CWDM channels are spaced widely.
oesn't need powerful laser.
Used for shorter/medium distances

OADM - Optical Add Drop Multiplexers.
EDFA - Erbium Doped Fiber Amplifier (used in DWDM to Amplify the signal)

Connectors

• GBIC - Giga Bit Interface Converter
  
• SFP - Small Form-factor Pluggable) - upto 4.25 Gbits/s
• XFP - 10 gig support for dieerent protocols
• SFP+ - 10 gig Ethernet and 8 gig FC, modified/updated XFP (SFP+ is small size, low power consumption, less expensive) .

Cable Connector type - (SC, LC are widely used)