FTLX1475D3BCL Product Specification
Finisar Corporation, April 2017 Rev. B1 Page 6
VIII. Digital Diagnostic Functions
Finisar FTLX1475D3BCL SFP+ transceivers support the 2-wire serial communication
protocol as defined in the SFP MSA1. It is very closely related to the E2PROM defined in
the GBIC standard, with the same electrical specifications.
The standard SFP serial ID provides access to identification information that describes the
transceiver’s capabilities, standard interfaces, manufacturer, and other information.
Additionally, Finisar SFP+ transceivers provide a enhanced digital diagnostic monitoring
interface, which allows real-time access to device operating parameters su ch as transceiver
temperature, laser bias current, transmitted optical power, received optical power and
transceiver supply voltage. It also defines a sophisticated system of alarm and warning
flags, which alerts end-users when particular operating parameters are outside of a factory
set normal range.
The SFP MSA defines a 256-byte memory map in E2PROM that is accessible over a
2-wire serial interface at the 8 bit address 1010000X (A0h). The digital diagnostic
monitoring interface makes use of the 8 bit address 1010001X (A2h), so the originally
defined serial ID memory map remains unchanged . The interface is identical to, and is thus
fully backward compatible with both the GBIC Specification and the SFP Multi Source
Agreement. The complete interface is described in Finisar Application Note AN-2030:
“Digital Diagnostics Monitoring Interface for SFP Optical Transceivers”.
The operating and diagnostics information is monitored and reported by a Digital
Diagnostics Transceiver Controller (DDTC) inside the transceiver, which is accessed
through a 2-wire serial interface. When the serial protocol is activated, the serial clock
signal (SCL, Mod Def 1) is generated by the host. The positive edge clocks data into the
SFP transceiver into those segments of the E2PROM that are not write-protected. The
negative edge clocks data from the SFP transceiver. The serial data signal (SDA, Mod Def
2) is bi-directional for serial data transfer. The host uses SDA in conjunction with SCL to
mark the start and end of serial protocol activ ation. The memories are organized as a series
of 8-bit data words that can be addressed individually or sequentially.
For more information, please see the SFP MSA documentation1,5 and Finisar Application
Note AN-2030.
Please note that evaluation board FDB-1027 is available with Finisar ModDEMO software
that allows simple to use communication over the 2-wire serial interface.