Hi Kai & Michael,
Thank you very much for your suggestions

Michael
When ground-filling around the opto isolators, you'll notice that rotating the top 4 optos gives better isolation. It will require re-thinking the resistor placement (a good thing also).

You are right michael rotating the top 4 optos certainly gives better isolation I have rotated them and posted the new layouts. The resistor has also been repositioned to improve the isolation.

Kai Klass
Remove the ground plane and signal lines under the opto couplers

Thank you ver much kai for your excellent suggestions.
I have removed the ground plane and signals under the optocoupler please check the new layouts and me let know is it ok now.

What I said right now, is especially valid for the signals arround the SSRs. If output side of SSRs can carry dangerous voltages, then you need to maintain a safety distance to microcontroller circuitry of at least 8mm. This is valid, if you use saftey class II power supply for your microcontroller board and if output side of SSRs is connected to mains voltage.

In the new layouts I have increased the separation in between the digital signals lines and the SSR AC terminals. Although this is at a cost of slight increase in the lengths of the digital traces. I have increased the separation between the SSR and ground plane. I have also moved the SSR's slightly towards right in order to increase the isolation.

3. Opto couplers are always prone to become damaged by voltage spike exceeding rated isolation voltage. As the coupling capacitance between input and output is very small, which is needed, of course, to limit interference coupled from one side to the other via charge injection, even little portions of charge, how they are observed with ESD events, can develop a destroying overvoltage.
Do always handle the opto coupler terminals, which are fed via your SUB-D connectors to outer world, as if they very very sensible points! Choose 'female' connector for your Sub-D connectors, so that pins cannot be directly touched.

Actually the SUB-D conenctors are outputs to stepper motor chopper drives and not inputs and I am using female conenctors for them. I am driving the stepper drives in sink mode. I have to sink approx 40mA through the SUB-D pins thus the reason for using opto is I can sink 40mA safely plus I get the isolation.

Another way to prevent the develop of destroying overvoltages at the isolation barrier, is to use the following scheme:

Let your PCB be device 'A' and let the equipement where you connect opto coupler signals to, be device 'B'. Connect both devices by shielded cables. Connect shields at the side of device 'B' to signal ground of device 'B'. I mean the ground, where the driver and reciever circuitry of otpo signals is connected to. Now cable shields carry signal ground of device 'B'.
On the other side of cables, namely at device 'A', connect the cable shield to chassis frame of SUB-D connectors. Connect all these SUB-D chassis frames together and connect them to signal ground of device 'A' via a varistor showing a threshold voltage of 500V, or so. Parallel the varistor by a resistor of 1MOhm.

This scheme works as follows:
If you connect device 'A' and 'B' by the help of this shielded cables, then any dangerous charge sitting on ground 'A' or 'B', perhaps from a former ESD event, will flow over the shield and via varistor from ground 'A' to ground 'B' (or vice versa). As consequence the stray capacitance of varistor will be charged up to the moment, where the threshold voltage (500V) is reached. Then, varistor becomes rather low ohmic and charge flows directly.
The effect of this protection scheme is, that any overstressing of isolation barrier of involved optocouplers is prevented. After the dangerous charge has flown, varistor is discharged to zero volts by the 1MOhm resistor.

This scheme must only be used, if both grounds ('A' and 'B') do not carry any dangerous potential, means if circuitry complies with safety class I or II standard!!

Excellent Idea, I will certainly implement this.