OCAM5 Flashcards
What are optical receivers?
Detectors that convert light pulses (wavelengths) into electrical signals
Key characteristics of an optical receiver?
1) Detect a broad spectrum of wavelengths
2) Efficiency of converting light to electricity
3) Ability to detect fast pulses
What type of detection do optical receivers use?
1) Direct
2) Coherent
Properties of direct detection? (3)
1) Uses photodiode to convert optical signal to electric current
2) Most commonly used
3) Used in systems up to 10 Gbps
Properties of coherent detection?
1) Recovers information from both electrical and magnetic fields of the optical signal
2) Paired with dual polarisation transmitters
3) Allows for greatest flexibility in modulation formats, providing access to both amplitude and phase information
How do receivers detect light?
Using semiconductor photodiodes as detectors, the photons are converted to an electrical signal. The data transmitted is extracted through additional processing of the electrical signal at the receive end.
What are the main types of optical detection components?
1) Photodiode
2) Coherent detector
What are the types of Photodiodes?
1) Positive-Intrinsic-Negative (PIN) photodiode
2) Avalanche Photodiode (APD)
Properties of PIN photodiode
1) Low cost
2) Reliable
Properties of APD photodiode
1) Provide amplification as well detection
2) Used in Long-haul networks
3) More accurate than PIN
4) But also more temp sensitive, complicated and expensive
Properties of Coherent detectors (6)
1) Used in conjunction with dual polarisation modulation schemes like DP-QPSK and QAM
2) support 40-100+Gbps DWDM line rates
3) support higher bit rates
4) Paired with digital signal processor (DSP) to process the converted electrical signal
5) Preserve phase information post detection, allowing for real time PMD compensation and dynamic CD compensation
6) Use multiple photo detectors to pull information from different polarisation states
