Bessel-Thomson reference filter 2.488 Gb/s / 2.5 Gb/s

The TA124 Bessel-Thomson Reference Filter is the highest-data-rate model in Pico Technology’s current Bessel-Thomson reference filter family. It is intended for engineers working with high-speed optical transmission systems, telecom interfaces and networking signals where receiver-oriented waveform characterisation is required.

Pico identifies TA124 for two standard data rates:

• 2.488 Gb/s for OC48 / STM16
• 2.500 Gb/s for InfiniBand 2.5G

It is used in the electrical path after optical-to-electrical conversion, not directly in the optical fibre path.

Correct Measurement Position

The correct measurement chain is:

Optical transmitter → Optical transmission path → O/E converter → TA124 Bessel-Thomson filter → Sampling oscilloscope

Pico states that connecting the appropriate BT filter between the O/E converter output and scope input enables the oscilloscope to display a waveform representative of what an equalised optical receiver would see.

This is the most important technical point to explain clearly on the product page.

Designed for 2.488 Gb/s OC48 / STM16

The TA124 supports the 2.488 Gb/s data rate associated with:

• OC48
• STM16
• SONET transmission systems
• SDH transmission systems
• Optical telecom interfaces
• Fibre-optic communication equipment

Typical measurement applications include optical transmitter analysis, eye-diagram evaluation, telecom interface verification and laboratory research.

Designed for 2.500 Gb/s InfiniBand 2.5G

The same TA124 reference filter is also specified for:

• 2.500 Gb/s
• InfiniBand 2.5G

This makes the accessory suitable for high-speed networking and communication measurements in addition to SONET/SDH optical testing. Pico explicitly maps both 2.488 Gb/s and 2.500 Gb/s applications to TA124.

Bessel-Thomson Reference Receiver Response

The TA124 should not be described merely as a generic signal filter.

Its role is to provide the appropriate reference receiver response for the selected communication rate.

This helps produce more meaningful measurements of:

• Eye opening
• Rise time
• Fall time
• Signal transitions
• Pulse shape
• Overshoot
• Undershoot
• Timing behaviour
• Receiver-oriented waveform quality

The filter limits the measurement response in a controlled way so the waveform is more representative of the communication receiver being modelled.

Optical Eye-Diagram Measurements

The TA124 is suitable for high-speed eye-diagram analysis after optical-to-electrical conversion.

Engineers can use the resulting waveform to study:

• Eye height
• Eye width
• Crossing position
• Transition quality
• Rise and fall behaviour
• Pulse symmetry
• Timing variation
• Signal quality

Using the correct bit-rate-specific reference filter is important because the measurement bandwidth can influence the apparent shape of the eye.

Compatible PicoScope Platforms

Pico Technology currently lists compatibility with:

• PicoScope 9221A
• PicoScope 9231A
• PicoScope 9321

These oscilloscopes are explicitly named by Pico for use with its Bessel-Thomson reference filter range.

Electrical Filter, Not an Optical Filter

The TA124 acts on the electrical signal after O/E conversion.

It should not be described as:

• An optical fibre filter
• An optical attenuator
• An optical-to-electrical converter
• An optical receiver
• A calibration standard
• A standalone measurement instrument

This distinction will improve both technical accuracy and search relevance.

Fixed Reference Filter

The TA124 is a fixed, data-rate-specific measurement accessory.

It does not need:

• USB control
• Software configuration
• PicoSDK
• User-selectable filtering
• Network connectivity
• Electronic switching

The required response is selected simply by choosing TA124 for the applicable communication rate.

Bessel-Thomson Filter Family

Pico currently lists the following family.

Why Correct Filter Selection Matters

Each filter in Pico’s BT family is matched to a specific serial data rate.

Choosing the wrong model can affect the apparent:

• Rise time
• Fall time
• Eye opening
• Pulse shape
• Overshoot
• Timing behaviour
• High-frequency waveform content

For OC48/STM16 at 2.488 Gb/s or InfiniBand 2.5G at 2.500 Gb/s, TA124 is the correct Pico reference filter.

Applications

The TA124 is suitable for:

• OC48 transmitter testing
• STM16 signal characterisation
• InfiniBand 2.5G testing
• Optical eye-diagram analysis
• SONET and SDH system development
• Optical transceiver testing
• Fibre-optic system validation
• Telecom equipment testing
• High-speed networking development
• Optical module characterisation
• Production optical testing
• Research and development
• University optical communication laboratories

Why Buy from RevineTech?

RevineTech can supply the TA124 for high-speed optical and telecom measurement setups and assist with selection of compatible PicoScope instruments, O/E conversion hardware and related accessories.