# WiSSL Gen 2 Concept Review

## Attendees

**MBARI:** David Caress, Jenny Paduan, Eric Martin, Chad Kecy, Francois Cazenave, Andy Hamilton, Paul Roberts, Ed Peltzer

**3D@Depth:** Carl Embry, Domenic Florin, Nelson Diaz, Jeremy Swedberg

## Presentation questions

1. EM: Do we need gigabit to get realtime? 
    1. DF: Target is to meet the 100mbps pipe
2. AH: LOS suffers when the bottom drops away?
    1. CE: not really that impactful
3. PR: What size buffer do you have? 
    1. DF: 10s, 4GS/s (DC asked on rate)
    2. PR: But what’s the bit depth, or dynamic range?
        1. DF: raw data is 100x bigger
4. EM: Dave it’s ok to limit picks to 3
    1. DC: yes, we rarely get better data past 3 hits
5. EM: How do upgrades happen?
    1. Depends on upgrade, some happen at factory, some remote
    2. Benefit of smaller design is easier shipping
6. DC: Dave would go down to 1 hit if it preserved high data rates.
7. DC: Where does this design diverge from standard products
    1. CE: Temperature
    2. CE: Lasers/Scanner, but faster laser would go into future products
    3. CE: Do not want to change electronics much
    4. CE: May be interested in bringing in wider swath, but currently in 3D’s critical path.
8. PR: You’re also increasing the rep rate, and a huge power increase, no? 
    1. The electronics dominate 
    2. Lasers going up 10x, 38mW would go 380mW
    3. PR: Can they go faster?
        1. yes but pulse energy drops
9. EM: How much risk is in the processing?
    1. Data size is the same as range points, so can trade.
    2. Requires less processing due to fewer points
    3. May have to do some post processing
10. PR: Is there margin in the analog to digital conversion?
    1. Will include a quality metric with temperature.
    2. Should be margin in A/D
11. PR: How many photons do you expect back?
    1. CR will get values back.
12. JP: On spatial averaging req to be uniform, what is that impact?
    1. DF: You will get a value back
13. EP: Are you time gating? Just the seafloor
    1. DF: Yes, but we are binning data to get a temperature profile.
    2. EP: The temperature will be very spread out, and this will be better for localizing
14. CE: What’s the size of a plume?
    1. 10cm at the emission source to 1m area
    2. Schwerin (wavy) patterns obvious near the source.
15. EP: Are you measuring at 2 wavelengths, or a band?
    1. 10-20nm band at varying spectra
    2. EP: How precisely do you know the wavelength?
        1. Well enough for Raman? 1 or 2 GHz is the bandwidth?
        2. 532.14 can see a 10 wavenumber shift in where the peak is, but a 10-20nm wide may be more tolerant in 
        3. Ed and Carl should follow up more on Wave number shifts and check that they’re going to sense the right values. 
    3. EP: no idea if these assumption work up at 350ºC ranges, also needs to be evaluated (CE agrees)
16. JP: Do we need to do calibrations at depth? 
    1. CE: A CTD has to be onboard, and then they can use that to calibrate shot to shot.
17. FC: What’s the window material?
    1. ND: Sapphire
18. FC: How did you get these numbers? FEA?
    1. Buckling: Thin wall equations
        1. Window not taken into account
    2. Yield: FEA
19. AH: Some questions about stress risers in the bond interfaces.
    1. FC: Very risky, especially due to cycling or temperature effects
    2. There is a set gap to allow for epoxy (.008”)
        1. They have a process to center it
20. AH: On dimensional stability, how much deflection in the window are you estimating, did you consider a ring?
    1. Minimizing deformation of glass to avoid depth related accuracies
21. FC: Points out the curved window risk, are you planning on a prototype?
    1. yes would like to propose this
22. PR: Would you grow the sapphire in this shape?
    1. It would be cut from a tube, but may be polarizing, and needs to be tested
    2. Have been in discussion with vendors on this
        1. They have not done this yet
23. AH: Why not do a ring of sapphire?
    1. 3D: Concerned about more stress on the epoxy bond
    2. FC: Cylinder would be more predictable.
    3. MBARI: Could a whole tube exist?
24. AH: Mounting concerns from the old system?
    1. CE: Have not considered mounting at this time.
25. MR: (Post Meeting review) Will PTP work on our gear?
    1. MBARI: Need to verify PTP works through Focal Fiber multiplexors at some point. It should on spec.

## Next Steps

1. Quote Detailed design, due July 13th
2. Quote Risk Reduction efforts for potential starts in 2022. 

## Relevant Materials

- [Presentation](https://mbari.sharepoint.com/:b:/r/sites/3DatDepth_MBARI/Shared%20Documents/MBARI_WiSSLG2ConceptReview_June2022-presented.pdf?csf=1&web=1&e=95PoVb)
- [Referenced Files](https://mbari.sharepoint.com/sites/3DatDepth_MBARI/SitePages/ProjectHome.aspx)