[time-nuts] opto coupler isolation?
Hi, An opto coupler seems good idea for an isolation amplifier but maybe not for the phase noise. Any experience? regards, henk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] opto coupler isolation?
Henk ten Pierick wrote: > Hi, > > An opto coupler seems good idea for an isolation amplifier but maybe > not for the phase noise. > Any experience? > > regards, > > henk > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > Henk The better optoisolators typically have a random jitter on the order of 50-100ps rms. This is considerably more than that for ACMOS logic (~1ps rms). Consequently the phase noise floor will be about 34 to 40dB higher than that when using ACMOS logic. Thus for low phase noise OCXOs using an optical isolator will significantly degrade the phase noise. An RF transformer is a lower phase noise solution to providing low frequency ground isolation. Achieving a reverse isolation of more than 140dB isnt too difficult with a few cascaded CB stages and a good layout combined with apprpriate shielding. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] opto coupler isolation?
In message <494882eb-d714-49b4-a7e2-bef04509d...@deriesp.demon.nl>, Henk ten Pi erick writes: >Hi, > >An opto coupler seems good idea for an isolation amplifier but maybe >not for the phase noise. Optocouplers have lousy dV/dt performance, so the jitter is horrible. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] opto coupler isolation?
Poul-Henning Kamp wrote: > In message <494882eb-d714-49b4-a7e2-bef04509d...@deriesp.demon.nl>, Henk ten > Pi > erick writes: > >> Hi, >> >> An opto coupler seems good idea for an isolation amplifier but maybe >> not for the phase noise. >> > > Optocouplers have lousy dV/dt performance, so the jitter is > horrible. > > Not true for the higher speed optoisolators (eg Avago's HCPL9000 series) In any case its more a matter of noise to slew rate ratio. The issue is really that the signal to noise ratio of the internal optical signal is relatively low. For better performance you need to use a higher power optical signal such as that from a single mode laser. However by the time you factor in the cost of the modulator etc its usually better to revert to a conventional design. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] opto coupler isolation?
Poul-Henning Kamp skrev: > In message <494882eb-d714-49b4-a7e2-bef04509d...@deriesp.demon.nl>, Henk ten > Pi > erick writes: >> Hi, >> >> An opto coupler seems good idea for an isolation amplifier but maybe >> not for the phase noise. > > Optocouplers have lousy dV/dt performance, so the jitter is > horrible. > Some optocouplers can be pretty good. Some even have 10s of km of pulled silica glas between the two sides. Some even have 1000s of km of pulled silica glas between them, and still have pretty OK dV/dt and noise. The cheap onces are really lousy thought. Cheers, Magnus - using several opto-couplers to get the message through ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] opto coupler isolation?
Hi, Thanks for the response, I did expect this. It saves me the experiment. henk On Jan 3, 2009, at 23:33, Bruce Griffiths wrote: > Poul-Henning Kamp wrote: >> In message <494882EB-D714-49B4-A7E2- >> bef04509d...@deriesp.demon.nl>, Henk ten Pi >> erick writes: >> >>> Hi, >>> >>> An opto coupler seems good idea for an isolation amplifier but >>> maybe >>> not for the phase noise. >>> >> >> Optocouplers have lousy dV/dt performance, so the jitter is >> horrible. >> >> > Not true for the higher speed optoisolators (eg Avago's HCPL9000 > series) > In any case its more a matter of noise to slew rate ratio. > > The issue is really that the signal to noise ratio of the internal > optical signal is relatively low. > For better performance you need to use a higher power optical signal > such as that from a single mode laser. > However by the time you factor in the cost of the modulator etc its > usually better to revert to a conventional design. > > Bruce > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
