OTN wave power balance method

  OTN wave power balance method

  Technical principle and system block diagram
OTN in multi-track long distance optical transmission, the transmission power difference would cause nonlinear effect, severely affecting system performance, allowing the system to port Pre-FEC and OSNR indicator cannot reach. Therefore, adjust the flatness of wave power is particularly important.

Block diagram of this system are as follows:

OSA for Spectrum Analyzer test point. The test Spectrum Analyzer model: EXFO FTB-500

first Ripple adjustments

Ripple tuning: tune into WR8/CWR8 by plus or minus decay value WSS wave power to reduce the flatness value of the port,

On WR8 first Ripple before entering the span adjustment after, as follows:

WR8 all waves of optical power statistics, calculate the average output power, wave power minus the average to be measured, rounded, multiplied by 10, minus the WSS port initial attenuation values to get Att:

Att=10*Int(Channel power-Ave(total per channel power))- WSS previous Att,

Att value, enter the following formula:

!dbgCutThru (FLTS 0 WRMACH AB) "config_chan C D Att 0"

---A-shelf, B-slot, c for -1, the D-Wave number for the WSS port to be tested.

All the waves in this root->dbgCut environment.

Objective: the attenuation values by setting the WR8/CWR8, all wave before entering the optical output power equal reach preliminary leveling, laying a solid foundation for subsequent adjustment.

Note: ROADM-SIG output power the bigger the better, if not more than BA receiver overloading optical power.

The transmitter output power set

Then began a flatness to span adjustment, operating at sending end of Span1 OA.

First of all, need to plan and set up the luminous power.

Luminous power of planning is important, involves the enforceability of subsequent operations, OTU Pre-FEC, and OSNR has great influence, and customers are very concerned about both of these parameters.

In practice, when the OSNR cushion and bit error rate before correction when not in compliance, you can optimize by reducing the luminous power bit error rate before correction.

Output optical power settings are based on the actual situation of no special requirements, generally set in 18~20dBm. All the span output power differential is not too big, the upper and lower range within 0.5dBm.

OA output can be calculated, in 80-wave system, for example, the following formula is available:

Take AM2318A for example: 10log80+X=23 X=4

AM2125A/B, for example, 10log80+X=21. X=2

OA =10log maximum output power (Current channel Numer) +X

Note: ZIC OA Line on the side of the output power has two readings: Total output power and Signal output power. General subject to Total output power.

1.3-tilt adjustment

Still operates in the span of the sending end OA. By setting the tilt value inclination of all wave power close to 0 (tilt value is usually set to a negative value, because the inclination angle before the adjustment is, to use a negative value to compensate).

3.2 and 3.3, and is completed within a span of flatness adjustment. Follow-up in the span is adjusted in accordance with 3.2 and 3.3.

1.4 Ripple over adjustment

After a couple of cross after the sometimes adjust the output power and tilt values is a flatness to achieve the desired values cannot be made, this requires one or more Ripple adjustment, even for individual and average optical power differences larger waves Ripple adjustments alone.

1.5 PA before entering the lower ROADM parameter settings

PA (before entering the ROADM OA) gain adjusted highs follow OA can reduce the noise figure.

At this point, between two ROADM flatness adjustment has been completed, subsequent ROADM between operations can be adjusted according to the 3.1~3.5. In practice, there are many unknown factors that may occur, so flatness adjustment is a very flexible operation, need to prescribe according to actual situation and experience are particularly important.