S.Q.M.P. is the hardware platform fitted with the Phase Hardware Module (PHM) and used by the Synchronization Quality Meter(SQM) to qualify the frequency stability of telecom networks and synchronization equipments (SSU, BITS , …).
Typically this is an instrument that characterizes the timing stability of a clock signal, by measuring the TIE (Time Interval Error) with respect to a Reference clock.
The TIE measurement circuitry, actually the phase error comparator, and the Reference clock are integrated into the PHM module. The processing of the TIE measurement is achieved by a classical PC running the SQM application software.
The results of each TIE measurement can be :
– monitored directly over time
– recorded in a file for post-processing, in order to achieve the ADEV – MDEV – TDEV – TIErms – MTIE quantities, according to ITU and ETSI Recs.
– compared with a ITU or ETSI maskchosen from a vast set stored in the instrument’s memory.
– sent to an external printer.
The clock under test can be a 2MHz G.703 signal, a 2Mb/s G.703 signal (framed G.704 or unframed), a 1.544Mb/s T1 signal (SF, ESF or unframed – with the optional T1 interface), or a 5MHz signal (announced).
The reference clock is generated by an inner Oscillator section, consisting of a DPLL(Digital Phase Locked Loop) which can be either locked to an external signal or free-running.
The external locking signal for the DPLL can be a 2MHz G.703 signal, a 2Mb/s G.703 signal (framed G.704 or unframed), a 5MHz signal, or a GPS signal coming from an optional additional module.
The DPLL is controlled by a Rubidium source; therefore, the frequency stability and accuracy of the Oscillator when free-running are in compliance with the G.812 class.
The S.Q.M.P. is also able to output the clock generated by the internal Oscillator. (available frequencies are 2 MHz G.703 signal – convertible to a 1.544Mb/s T1 signal with the optional T1 interface- and 5MHz). As a consequence, the S.Q.M.P. can also offer synchronization signal to telecom network equipments in a way similar to a Synchronization Supply Unit (SSU)