Pin Description

The QSFP28 pin assignment is SFF-8679 compliant.

QSFP28 Pin Description 100Gb/s End

Pin	Symbol	Description	Pin	Symbol	Description
1	Ground	Ground	20	Ground	Ground
2	Tx2n	Connected to Port 1 lane Rx2 Inverted Data	21	Rx2n	Connected to Port 1 lane Tx2 Inverted Data
3	Tx2p	Connected to Port 1 lane Rx2 Non-Inverted Data	22	Rx2p	Connected to Port 1 lane Tx2 Non-Inverted Data
4	Ground	Ground	23	Ground	Grounds
5	Tx4n	Connected to Port 2 lane Rx2 Non-Inverted Data	24	Rx4n	Connected to Port 2 lane Tx2 Inverted Data
6	Tx4p	Connected to Port 2 lane Rx2 Inverted Data	25	Rx4p	Connected to Port 2 lane Tx2 Non-Inverted Data
7	Ground	Ground	26	Ground	Ground
8	Mod-SelL	Cable Select	27	ModPrsL	Cable Present
9	ResetL	Cable Reset	28	IntL	Interrupt
10	Vcc Rx	+3.3V Power supply receiver	29	Vcc Tx	+3.3V Power supply transmitter
11	SCL	2-wire serial interface clock	30	Vcc1	+3.3V Power Supply
12	SDA	2-wire serial interface data	31	LPMode	Low Power Mode
13	Ground	Ground	32	Ground	Ground
14	Rx3p	Connected to Port 2 lane Tx1 Non-Inverted Data	33	Tx3p	Connected to Port 2 lane Rx1 Non-Inverted Data
15	Rx3n	Connected to Port 2 lane Tx1 Inverted Data	34	Tx3n	Connected to Port 2 lane Rx1 Inverted Data
16	Ground	Ground	35	Ground	Ground
17	Rx1p	Connected to Port 1 lane Tx1 Non-Inverted Data	36	Tx1p	Connected to Port 1 lane Rx1 Non-Inverted Data
18	Rx1n	Connected to Port 1 lane Tx1 Inverted Data	37	Tx1n	Connected to Port 1 lane Rx1 Inverted Data
19	Ground	Ground	38	Ground	Ground

QSFP28 Module Pad Layout

QSFP28 Pin Description 50Gb/s End

Pin	Symbol	Description	Pin	Symbol	Description
1	Ground	Ground	20	Ground	Ground
2	Tx2n	Connected to lane Rx2 Inverted Data	21	Rx2n	Connected to lane Tx2 Inverted Data
3	Tx2p	Connected to lane Rx2 Non-Inverted Data	22	Rx2p	Connected to lane Tx2 Non-Inverted Data
4	Ground	Ground	23	Ground	Grounds
5	Not connected	Not connected	24	Not connected	Not connected
6	Not connected	Not connected	25	Not connected	Not connected
7	Ground	Ground	26	Ground	Ground
8	Mod-SelL	Cable Select	27	ModPrsL	Cable Present
9	ResetL	Cable Reset	28	IntL	Interrupt
10	Vcc Rx	+3.3V Power supply receiver	29	Vcc Tx	+3.3V Power supply transmitter
11	SCL	2-wire serial interface clock	30	Vcc1	+3.3V Power Supply
12	SDA	2-wire serial interface data	31	LPMode	Low Power Mode
13	Ground	Ground	32	Ground	Ground
14	Not connected	Not connected	33	Not connected	Not connected
15	Not connected	Not connected	34	Not connected	Not connected
16	Ground	Ground	35	Ground	Ground
17	Rx1p	Connected to lane Tx1 Non-Inverted Data	36	Tx1p	Connected to lane Rx1 Non-Inverted Data
18	Rx1n	Connected to lane Tx1 Inverted Data	37	Tx1n	Connected to lane Rx1 Inverted Data
19	Ground	Ground	38	Ground	Ground

QSFP28 Module Pad Layout

The pinout of the 50Gb/s ends of the cable is identical to the 100Gb/s end except that RF lanes 3 and 4 (pins 5, 6, 14, 15, 24, 25, 33, 34) are not connected.

Last updated: January 28, 2024