[AusNOG] Reference clock for SDH network

Peter Childs pchilds at internode.com.au
Tue Oct 27 15:29:14 EST 2009

On 27/10/2009, at 2:37 PM, Daniel O'Connor wrote:

> On Tue, 27 Oct 2009, Damien Gardner Jnr wrote:
>> On 27/10/2009, at 12:19 PM, Tom Storey wrote:
>>> Hi All,
>>> Can anyone suggest a clock that is able to produce a 2mbit/2mhz
>>> sync signal to use as a reference for an SDH network?
>>> The network is detatched from any existing SDH networks, so I have
>>> to clock it from scratch.
>>> So far I have only come across one that is around the $3k mark
>>> (Oscilloquartz), and my googlefu is failing me at the moment.
>> I'm obviously missing something here, but how on earth can a crystal,
>> a couple of caps and resistors, and maybe a transistor or two or an
>> IC work out to the $3k mark??
>> I'm assuming you're actually looking for something more complex than
>> a simple 2mhz clock signal??
> Depends what level of jitter and stability you need.
> A rubidium conditioned signal source could easily cost that much.
> If the jitter and stability aren't a big issue then a $5 XTAL from
> Jaycar will do though ;)

A PRC for SDH should follow G.811

'The maximum allowable fractional frequency offset for observation  
times greater than one week is 1 part in 10, over all
applicable operational conditions.'

'The intrinsic jitter at 2048 kHz and 2048 kbit/s output interfaces as  
measured over a 60-second interval shall not
exceed 0.05 UIpp when measured through a single pole band-pass filter  
with corner frequencies at 20 Hz and 100 kHz.'

I guess the target market determines the 'market-bears' price.

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