ONET8551T: about different waveform of theonet8551t

Hello Cickey,

Can you provide an explanation for every color trace on the screen shots? Do you have a trace that shows the optical input power?  

Is the ONET part enabled the whole time? 

Is it possible that the shutdown time is due to the optical source?  Our laser does not turn on or off fast, so we have not measured this response. 

Regards,

Loren

hi，loren，

the query had been got。

the red trace is on behalf of t he negative output of the onet8551，and the blue trace is behalf of positive output of the onet8551；

the yellow trace is behalf of the optical  enable signal，low level rerepresent  a light signal input，high level represent shutdown the light input；

diagram as below。

 the customer mainly care  the max delay time is how much？

and different power signal input，the output  amplitude weather same？if different，the max and min amplitude is how much‘？

many thanks！

best regards

cickey xu

Hi Cickey,

It looks like even though the optical source is disabled, it takes a while for the optical source to completely shut-down (or no light) from the moment it is disabled. Higher the optical power output present from the optical source, the longer it would take for the optical source to completely shut-down (or no light) from the moment it is disabled.

The ONET8551T is a limiting amplifier, where the differential output voltage is fixed beyond a certain input power level. So, if the optical source takes some finite amount of time to turn-off depending upon its power level (longer time to turn-off for higher power level), then the ONET8551T outputs will be on for the same duration until it is no more limiting and eventually turn off.

Best Regards,

Rohit

dear rohit；

I see, thank you very much for your reply！

give you a big thumbs up！

hello，Rohit Bhat,

firstly thanks for your Wonderful reply！

my customer had  knew the  reason，but they also want to know the longest delay time is how long？

In the graphic above，the yellow trace from low level to high leve  represent  the power input signal from open to completely close； that is to say，when the yellow trace become high level ，the power input signal completely shutdown；

can you give me the longest delay time？it is equivalent of our ont8551 transient。

very thanks！

Hi Cickey,

The ONET8551T has 9GHz bandwidth, which means the rise/fall time of the signal is tr = 0.35/BW = 39psec. So, it does not really explain that the TIA would be adding usecs of delay time at the output when the input signal is shut-down completely.   

I feel that even though the laser is completely shutdown or disabled, there is still some residual power or light present at the ONET8551T input which causes its outputs being present in the usec duration depending upon the input power level. 

Best Regards,

Rohit

hi,ohit,

  thank for your reply。

 I will explain the case to my customer，if there are any  ohter questions ,I may also bother you.

many thanks.

cickey xu

 

 

 

hi，rohit bhat；
l'm sorry for bothering you again；
my customer also consult our device shutdown delay time is how long？
in the different input signal power（such as -1db，-5db，-10db，-15db），My client admitted that this delay contains light delay（The light from a light to shut off completely）, but the light signal delay basic fixed, in about 30 us, and can be seen from the four figure, under different input signal, the total delay time is not the same;As a result, the client mean total delay time minus the optical signal delay, delay time of the rest of the time is our devices delay, equivalent to our turn off time of the device from a light signal to shut off completely，my client want to know this delay time is how long？（min and max delay time is how long ）

Looking forward to your reply！

thank you very much。


best regard

cickey xu

Hi Cickey,

No problem. Do you know how are they shutting down the whole ONET8551T device? I don't think there is a power down pin on the device. Also, do you know about the type of laser they are using? It would be good to know the laser part number.

As I mentioned earlier, if the ONET8551T device is powered on, the device will not add usec of delay time at the output when the input signal is completely shut-down. There will be some dependence of the device outputs being shut-down differently (in < 100 nsec range) based on the different input signal power level; but not anywhere close to what the customer is recording (in ~150usec range for -1dBm input power level).  

Best Regards,

Rohit