Understanding Optical Stressed Receiver Sensitivity

This article delves into the concept of Stressed Receiver Sensitivity within the optical domain. We’ll explore its definition, its significance in optical power budget calculations, and the factors that influence it.

What is Stressed Receiver Sensitivity?

Stressed Receiver Sensitivity is defined as the minimum optical average power required at the input of an optical receiver to achieve a specified Bit Error Rate (BER). In simpler terms, it’s the lowest power level the receiver can handle while still functioning correctly.

This parameter is crucial for designing and analyzing optical communication systems. It plays a key role in determining whether a system will perform adequately under varying conditions.

Why is it Important?

Stressed Receiver Sensitivity is a vital parameter in optical power budget calculations. These calculations help determine the maximum distance a signal can travel, or the amount of loss that can be tolerated before the signal quality becomes unacceptable. Knowing the receiver’s sensitivity allows engineers to plan their optical networks with precision.

What Affects Stressed Receiver Sensitivity?

Several factors can degrade a receiver’s sensitivity. These impairments include:

• ISI (Inter-Symbol Interference): Distortion caused by overlapping symbols.
• Jitter: Variations in the timing of a signal.
• Rise Time and Fall Time: The time taken for a signal to transition from low to high and vice versa.
• RIN (Relative Intensity Noise): Noise generated by the transmitter.

These impairments essentially reduce the receiver’s ability to differentiate between distinct signal levels, thus requiring a higher input power.

Optical Receiver Model

Here’s a simplified model of a typical optical receiver:

As you can see, it generally consists of:

• Photo-diode: Converts light into electrical current.
• Transimpedance Amplifier (TIA): Amplifies the weak current from the photodiode and converts it to a voltage.
• Limiting Amplifier (LA): Amplifies the signal to a consistent level.
• Clock-Data Recovery Module (CDR): Extracts clock and data from received signal.

The Formula for Stressed Receiver Sensitivity

The Stressed Receiver Sensitivity is often calculated using the following formula:

Let’s break down the components:

• OMA (Optical Modulation Amplitude): This is the peak-to-peak current at the TIA input divided by the photo detector responsivity (ρ), measured in A/W.

  • It can be expressed as: OMA = IP-P / ρ (µW)

• re: This is the extinction ratio of the received optical signal, which indicates the ratio between the power levels of the ‘1’ and ‘0’ bits.

Understanding these terms and how they relate is vital for comprehending how optical receivers perform in real-world conditions.