Finisar AN-2030 - Manual (Page 11)

AN-2030: Digital Diagnostic Monitoring Interface for Optical Transceivers
F i n i s a r
9/26/02 Revision D Page 11
Vendor Rev 1
The vendor revision number (vendor rev) is a 4-byte field that contains ASCII 2
characters, left-aligned and padded on the right with ASCII spaces (20h), defining the 3
vendor’s product revision number. A value of all zero in the 4-byte field indicates that 4
the vendor rev is unspecified. All legacy Finisar transceivers contain zero in all 4 bytes 5
or ASCII space (20h) in all four bytes or one of two place holders: “X1—“ or “1A—“. 6
Early versions of the digital diagnostic standard (SFF-8472), used a scale factor of 7
1µA/AD Count for interpreting laser bias current readings. SFF-8472 later changed the 8
scale factor to 2µA/AD Count. All Finisar modules using a scale factor of 2µA/AD Count 9
have an ASCII “A” written in byte 56 of this field. 10
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Laser Wavelength 12
Nominal transmitter output wavelength at room temperature. This field is a 16 bit value 13
with byte 60 as high order byte and byte 61 as low order byte. The laser wavelength is 14
equal to the the 16 bit integer value in nm. This field allows the user to read the laser 15
wavelength directly, so it is not necessary to infer it from the transceiver “Code for 16
Electronic Compatibility” (bytes 3 – 10). This also allows specification of wavelengths 17
not covered in bytes 3 – 10, such as those used in coarse WDM systems. 18
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DWDM Wavelength Fraction 20
Byte 62 is reserved (set to 00h) in the SFP MSA as well as SFF-8472. Finisar DWDM 21
transceivers use this byte in conjunction with bytes 60-61 to indicate the DWDM 22
transceiver laser wavelength. Bytes 60-61 provide the integer wavelength in units of 23
nm. In DWDM transceivers, by 62 provides the fractional wavelength in units of 24
0.01nm. Thus the wavelength for a particular DWDM transceiver is given by: 25
(byte 60,61) + (byte 62 * 0.01nm). In all non-DWDM Finisar transceivers, this byte is set 26
to 00h. 27
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CC_BASE 29
The check code is a one byte code that can be used to verify that the first 64 bytes of 30
serial information in the SFP is valid. The check code shall be the low order 8 bits of the 31
sum of the contents of all the bytes from byte 0 to byte 62, inclusive. 32
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