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OTDM vs OWDM | Difference between OTDM and OWDM

This page compares OTDM vs OWDM optical multi-channel systems. It mentions difference between optical time domain multiplex (OTDM) and optical wavelength domain multiplex (OWDM). It also mentions advantages and disadvantages of both the optical systems.

Both OTDM and OWDM are used as optical multi-channel systems. Optical multiplexing is realized in either time domain or wavelength domain. The one realized in time domain is referred as OTDM which is done using ultra short pulse transmission. The one realized in wavelength domain is referred as OWDM which is done using large number of carrier wavelegnths in the same fiber.
Refer Tutotial on fiber optical communication➤.

OTDM-optical time domain multiplex


In the OTDM optical multiplexing type, different data channels occur in time domain. They are placed in non-overlapping bit time slots T. All these slots are totally overlapped in optical frequency domain. There will not be any crosstalk in time domain in the OTDM.

OWDM-optical wavelength domain multiplex


In the OWDM optical multiplexing type, different data channels occur in frequency domain. They are placed in non-overlapping frequency bands ( Bch ) . All these channels can totally overlap in time domain without any crosstalk.
Refer Tutorial on DWDM system basics➤.

Full form Optical Time Division Multiplex Optical Wavelength Division Multiplex
Advantages System is very simple to implement. The components in the system are simple.
Disadvantages There are challenges in fucntioning of device components involved in switching. Dispersion is the great concern here. There is high component count requirement. Wavelength conversion is the great challenge.
Key optical components Mode locked lasers, all optical DEMUX, dispersion comp. Optical DEMUX, narrowband filters, single frequency sources etc.
Application Long and short distances. Long distance, LANs.

Both the optical multiplexing types are using following optical components in the system.
• Optical Modulator and demodulator
• Optical Multiplexer and De-Multiplexer
• Laser Pulse generator at transmit end
• Photodetector at receive end
• Optical Amplifier to enhance signal strength
• Clock extraction at the receiver which is used to extract the information at receiver
• Wavelength filters to extract desired wavelengths
Refer links to basics on various Optical Components➤.

Advantages and Disadvantages of OWDM

• relative low data rate per optical channel with modest requirements for dispersion and electronic speed
• data format and timing of the channels are independent of each other

• Challenging requirements for the wavelength MUX and DEMUX with respect to wavelength control, filter characteristics (Δλ~0.5-1.2 nm), cross talk and thermal stability.
• large component count.
• highly stable optical frequency generation and small oscillator bandwidth (~MHz).
• high total operational power (Nopt x Pop,channel; typ. 200 x 1mW/ch=200mW) in the fiber can result in optical nonlinearities.


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