IAM Electronic - Instrumentation And Measurement Electronics FMC SFP Adapter 

DS#T0012 REV 2022/05/19 
PDF version (coming soon), HTML version

SFP Adapter Board for Low-Pin Count
FMC Connectors

  • Breakout of SFP connector
  • Data rates up to 4 Gb/s
  • ANSI/VITA 57.1 compliant
  • Commercial grade form factor
  • Low-pin count (LPC) connector
  • Selectable I2C bus voltage (VADJ or 3P3V)
  • Open-source hardware
FMC SFP Adapter Board

FMC SFP Adapter Board with components on bottom
FMC SFP Adapter Board top side
  • 1000BASE-X data links
  • Board-to-board connections
  • Testing and debugging of SFP transceivers
  • Easy prototyping
  • Loopback testing
  • Research and education with FPGAs

1. Description

The FMC SFP Adapter Board is a passive adapter for accessing the multi-gigabit transceiver data pair of the FMC low-pin count (LPC) connector. The DP0_C2M and DP0_M2C data pairs are connected to the 20-pin SFP board connector inside the single-port SFP cage. The board supports data rates up to 4 Gb/s, and is ideally suited for 1000BASE-X applications (Gigabit Ethernet transmission over fiber). An on-board oscillators provides a reference clock of 125.000 MHz to the GBTCLK signal pair (clock signal for multi-gigabit transceiver data pair). All electrical signals of the SFP transceiver are accessible via the FMC-LPC connector or test points on the PCB. No configuration of the card is necessary for easy startup.

2. Application information

1. Loopback test
The modules can be used in a loopback test to check the components of a board-to-board connection. These tests are useful for evaluating an FPGA test design on carrierboard or transceiver tests. We have tested the FMC SFP adapter with various SFP optical transceivers.
SFP Transceivers for FMC SFP Adapter
Fig. 1: SFP transceivers used for testing the FMC SFP adapter.

Our test have been carried out with two FMC carrier boards with Xilinx FPGAs (fig. 2). We use the Xilinx IBERT core for loopback testing. The "far end PMA" loopback mode must be enabled on one of the boards.
FMC SFP Adapter loopback test
Fig. 2: FMC loopback configuration with two carrier boards and two FMC SFP adapter modules.

The eyediagrams for different transceivers and data rates are shown in fig. 3 .. 5
Eyediagram 1000BASE SFP with 1250 Gigabit/s
Fig. 3: Eyediagram from Xilinx IBERT with 1000BASE SFP Transceivers in loopback configuration with 1.25 Gb/s.

Eyediagram 10G SFP+ with 1250 Gigabit/s
Fig. 4: Eyediagram from Xilinx IBERT with 10G SFP+ Transceivers in loopback configuration with 1.25 Gb/s.

Eyediagram 10G SFP+ with 3750 Gigabit/s
Fig. 5: Eyediagram from Xilinx IBERT with 10G SFP+ Transceivers in loopback configuration with 3.75 Gb/s.

During all tests, we did not receive a single bit error. The bit error rate (BER) was also checked with the Xilinx IBERT core (fig. 6).
Bit error rate with FMC SFP adapter
Fig. 6: The bit error rate of the FMC SFP adapter with a 10G SFP+ transceiver in loopback mode at 3.75 Gb/s.

3. Electrical data (pin description)

The printed circuit board is open-source hardware! You can download the FMC LPC SFP Adapter board schematics and PCB layout files in their latest revision from http://www.fmchub.com.

3.1 Pinout of the FMC LPC Connector

Fig. 7 and tab. 1 show the connections of the signals on the FMC connector P1

Pin assignments of the FMC SFP Adapter

Fig. 7: Pin assignments of the FMC LPC connector P1.

Tab. 1: Pin assignments of the FMC SFP Adapter Board.
FMC pin name FMC pin designator SFP pin name
GBTCLK0_M2C_PD4125 MHz clock + (to FPGA)
GBTCLK0_M2C_ND5125 MHz clock + (to FPGA)


The EEPROM for storing FMC FRU (field replaceable unit) information is an M24C02 with 2 Kbit (256 Byte). The FRU record determines the voltage on the VADJ rail of the FMC connector. By default, the FRU EEPROM is programmed to request 3.3 V from the carrier board. Further, the memory stores the board information such as manufacturer name and product number. The device can be read and written by the I2C interface of the FMC connector (Pins C30 and C31). The FMC SFP Adapter Board includes 4K7 pull-up resistors on the SCL and SDA signal lanes. The I2C address of the M24C02 is defined by the GA0 and GA1 pins of the FMC connector in accordance with the ANSI/VITA57.1 standard.

4. Mechanical data

The board outline is defined by the ANSI/VITA 57.1 standard for single width FMC modules. FMC SFP Adapter mechanical data

FMC SFP Adapter mechanical data

Fig. 8: Mechanical drawing of the FMC SFP Adapter board.

The mounting holes are plated but have no electrical connection. Their sizes and positions are in accordance with ANSI/VITA 57.1 single width FMC modules.

5. Ordering information
The FMC SFP Adapter Board can be ordered at various online market places, or you can request a quotation by sending an e-mail to info@iamelectronic.com.

Tab. 5: Assembly variants of FMC SFP Adapter board with product numbers and market places.
Product no. Description Market place Request quote Standard lead time
T0012 FMC LPC SFP Adapter Board with
MC-LPC-10 connector, SFP connector with cage and clock generator
on bottom side.
IAM Electronic Shop

Ebay #185439240058


info@iamelectronic.com Normally in stock, otherwise 3 weeks

6. Ressources
[1] Schematics: FMC_SFP_ADAPTER.pdf
[2] Github repository: https://github.com/FMCHUB/FMC_SFP_ADAPTER

7. Document history
Document number:

Version history:
2022/24/05: Update links for schematics and Github repository, Ebay and Tindie article listings
2022/19/05: New content in section mechanical data
2022/19/05: New content in section application information (1. loopback test)
2022/18/05: Initial release

8. Imprint
Name and registered office of the company:
IAM Electronic GmbH
Bucksdorffstr. 43
04159 Leipzig

Phone: +49 341 26496031
E-Mail: info@iamelectronic.com

Chief Executive Officer: Dr. Philipp Födisch

Commercial register:
Register court: Amtsgericht Leipzig
Register number: HRB 34071
Value Added Tax Identification Number: DE313797981