What is Bit Rate vs. Baud Rate?

Summary

This video explains the difference between bit rate and baud rate in optical transmission systems. Bit rate refers to the amount of data transmitted per second, while baud rate refers to the number of symbols transmitted. In binary transmission, both rates are the same, but in modern systems like coherent optical transmission, the bit rate is higher due to advanced modulation techniques that allow multiple bits per symbol. The video also explores the role of polarization and sophisticated modulation in achieving high-speed data transmission, such as 800 Gbps in cutting-edge systems like Infinera's I6.

Takeaways

• 😀 Bit rate refers to the amount of data transmitted per unit of time, typically measured in bits per second (bps).
• 😀 Baud rate is the number of symbols transmitted per unit of time, and it’s often confused with bit rate but they are not the same.
• 😀 Bit rate and baud rate apply to various data transmission systems, including wireless networks, cable modems, and fiber optics.
• 😀 In binary transmission, one bit is transmitted per symbol, and bit rate equals baud rate.
• 😀 For more complex transmission schemes, bit rate exceeds baud rate because multiple bits are encoded into each symbol.
• 😀 Coherent optical transmission systems use advanced techniques like quadrature phase shift keying to transmit multiple bits per symbol.
• 😀 Quadrature phase shift keying (QPSK) allows the transmission of 2 bits per symbol, doubling the bit rate compared to binary transmission.
• 😀 Modern 800 Gbps coherent optical engines, such as Infinera's I6, can transmit up to 100 billion symbols per second.
• 😀 Some transmission schemes use polarization to double transmission capacity, helping achieve over a terabit per second of raw transmission.
• 😀 Despite high raw transmission rates, overheads for tasks like framing and error correction reduce the usable bit rate to 800 Gbps in some systems.
• 😀 The key takeaway is that in complex transmission systems, the bit rate exceeds the baud rate because each symbol carries more than one bit of information.

Q & A

What is the difference between bit rate and baud rate?

Bit rate refers to the amount of data transmitted between two devices per unit of time, typically measured in bits per second. Baud rate refers to the number of symbols transmitted in the same time frame.

Can baud rate and bit rate ever be the same?

Yes, baud rate and bit rate are the same only in binary transmission schemes, where each symbol represents one bit.

What are some examples of data transmission systems mentioned in the script?

The script mentions data transmission over 5G wireless networks, hybrid fiber coax networks for cable modems, and coherent optical transmission systems over fiber optic networks.

How does binary transmission work in fiber optics?

In binary transmission over fiber optics, a laser is turned on to represent a '1' and off to represent a '0'. The rate at which these signals are transmitted determines the bit rate.

What is the bit rate achieved with binary transmission at one billion pulses per second?

At one billion pulses per second, a binary transmission achieves a bit rate of one gigabit per second.

How do modern coherent optical transmission systems improve upon binary transmission?

Modern systems use sophisticated modulation techniques such as quadrature phase shift keying (QPSK) and polarization, allowing multiple bits to be sent per symbol, effectively increasing the bit rate.

What is quadrature phase shift keying (QPSK)?

QPSK is a modulation scheme in which the laser is set to one of four states, allowing two bits of information to be sent per symbol, which increases the bit rate.

What is the baud rate of an 800 gigabit per second coherent optical engine?

The baud rate of the 800 gigabit per second coherent optical engine is 100 billion symbols per second.

How does polarization affect the transmission capacity of modern optical engines?

Polarization allows modern optical engines to double their transmission capacity, enabling more data to be transmitted simultaneously.

What is the usable bit rate of an 800 gigabit per second coherent optical engine after overhead is subtracted?

The usable bit rate of the 800 gigabit per second coherent optical engine is 800 gigabits per second after subtracting internal overhead for functions like framing and error correction.