步骤:
1.先运行,porterrshow 查看口状态，然后‘statsclear‘ and ‘slotstatsclear‘
2.查看:porterrshow,看下port 口的情况
3.收集supportshow ,supportsave
4.查看sfpshow -all 可以看23口倒数第二行RX Power状态，若较大就正常
  sfpshow -all       :

=============
Port  0:
=============
Identifier:  3    SFP
Connector:   7    LC
Transceiver: 540c402000000000 200,400,800_MB/s M5,M6 sw Inter_dist
Encoding:    1    8B10B
Baud Rate:   85   (units 100 megabaud)
Length 9u:   0    (units km)
Length 9u:   0    (units 100 meters)
Length 50u:  5    (units 10 meters)
Length 62.5u:3    (units 10 meters)
Length Cu:   0    (units 1 meter)
Vendor Name: BROCADE        
Vendor OUI:  00:05:1e
Vendor PN:   57-1000012-01  
Vendor Rev:  A  
Wavelength:  850  (units nm)
Options:     001a Loss_of_Sig,Tx_Fault,Tx_Disable
BR Max:      0  
BR Min:      0  
Serial No:   UAA210473397682
Date Code:   101127 
DD Type:     0x68
Enh Options: 0xf0
Status/Ctrl: 0x92
Alarm flags[0,1] = 0x0, 0x0
Warn Flags[0,1] = 0x0, 0x40
                                          Alarm                  Warn
                                      low        high       low         high
Temperature: 34      Centigrade     -15         100        -10         95
Current:     7.112   mAmps          2.000       8.500      2.000       8.500 
Voltage:     3286.1  mVolts         2800.0      3800.0     2970.0      3630.0
RX Power:    -7.2    dBm (190.9 uW) 0.0    uW   6550.0 uW  49.0   uW   1100.0 uW
TX Power:    -2.3    dBm (588.7 uW) 50.0   uW   800.0  uW  100.0  uW   700.0  uW

5.若还是很小，原来：-16.3   dBm (23.2  uW)，更换光纤线，再重复上面的步骤