Lightwave Logic Inc (LWLG)

[Photonics_Guy]

Pros & Cons of 1310nm vs 1550nm

I see some questions about the 1310nm band vs 1550nm, so I'll address a few advantages and disadvantages of each.

Single-Mode Fiber (SMF) gets lossy between 1350nm and 1450nm. That means that there will be significant (unacceptable) optical signal loss between those wavelengths. Consequently, the industry has designated standard operating wavelengths directly above and below this lossy region. Hence, the use of 1310nm and 1550nm wavelengths.

Here are some good charts from a Finisar presentation in Sept 2017.

Lossy region between 1350nm and 1450nm



Here, we see the optical signal loss peaking around 1400nm. You can see from the chart that, at 1310nm and 1550nm, the fiber losses are minimal.


Insertion Loss (IL) of 1310nm vs 1550nm



This chart shows typical fiber losses per distance for both 1310 and 1550nm wavelengths. At and above 10km the fiber loss for 1310nm becomes unacceptable. Consequently, 1310nm is not used for long-haul networks.


Dispersion of 1310nm vs 1550nm



1550nm suffers from Dispersion more so than 1310nm wavelengths. Dispersion causes the modulated signal to degrade over distance due to a phenomena closely related to group delay, i.e., different frequencies travel at different rates through the fiber. This results in signal edges getting distorted (rounded off), which affects the integrity of the eye-diagram. This manifests as higher bit-error rate (BER) as distance increases. While this chart shows that 1310nm has better dispersion characteristics than 1550nm, 1310's fiber losses mentioned above preclude it from being used for long haul networks.


Phase Detector Responsivity of 1310nm vs 1550nm



At the end of every photonics transmission line is a photo-detector (PD) [AM modulation] or a phase detector [phase modulation] to recover the modulated RF signal. The PD is typically the device that sets the floor for the sensitivity of the transmission link. 'Responsivity' is a measure of the PD sensitivity. The higher the responsivity, the more sensitive it is to detecting low-amplitude signals and - consequently - the better the dynamic range of the system. At 1310nm, PDs have improved responsivity vs 1550nm, which provides for improved dynamic range. Again, regardless of 1310's improved responsivity in PDs, its insertion loss over distances above 10km limits this advantage.


Conclusions:

Addressing the 1310nm markets opens up the <10km market for LWLG devices, as that wavelength is almost exclusively used for those markets. The recent PR is good news. LWLG's challenge remains to get tested/validated devices in the hands of potential providers and customers that service those markets. LWLG appears to have the technical know-how and IP to make it happen. It's wonderful to see cool developments in the lab. The question is can they translate these nifty developments into products and/or tech transfer agreements that are financially rewarding to the company and shareholders? Time will tell.

PG