Passive optical components, which operate without power, offer an effective and dependable approach for optimizing bandwidth while conserving fiber usage. In the past, passive technologies like wavelength-division multiplexing (WDM) found applications in long-distance and intercontinental submarine cable data transmission. In recent times, the reach of WDM has extended to the periphery, and passive optical networks (PONs) utilizing WDM have taken the lead in facilitating fiber-to-the-home(FTTH), and the latest fiber-to-the-room(FTTR). There is happening in 5G wireless network fronthaul also, in C-RAN and O-RAN fronthaul architecture, WDM is the must device to build a perfect network.

Contemporary telecommunications networks encompass a variety of passive devices. These include WDM, splitter, add/drop OADM, optical switch, VOA, as well as fiber distribution solutions, among others. In planning out your CWDM and/or DWDM network, there are 6 questions to consider and discuss with your passives partner.

1.CWDM or DWDM

Coarse WDM (CWDM):  CWDM is defined by WDM systems with fewer than 18 active wavelengths per fiber, from 1270nm to 1610nm, 20nm channel spacing. CWDM is used for short-range communications, no optical amplifier in the fiber link, so it employs wide-range frequencies with wavelengths that are spread far apart. CWDM is a compact and cost-effective option when spectral efficiency is not an important requirement.

Dense WDM (DWDM):  DWDM’s tighter wavelength spacing fits more channels onto a single fiber, but costs more to implement and operate. DWDM dices spectrum finely, fitting 40, 44, 80, 88, 96 channels or more into the C-band frequency range. The most mainstream is 100GHz C-band, but now the O-band DWDM is applied in 5G fronthaul, and 75GHz C-band for 400Gbps network, 100GHz C+L-band for capacity exhaustion, are discussing and using in some application.

Figure 1, The spectrum of CWDM and DWDM

2.Single or Dual fiber

WDM multiplexer is bi-directional, as the light in fiber is bi-directional, they can be used as a Mux or a Demux, or both.

If limited to a single fiber, a single module can multiplex the designed channels on one end and demultiplex them at the other end with another single module. Alternatively, you can mux half of your channels in one directoin and demux half of them in the other. If you have two fibers to work with, using a twin module Mux&Demux, you can multiplex all your channels onto one fiber and demultiplex all of the channels coming in on another fiber.

There is one guess game of price, to understand the Mux/Demux, and Mux&Demux, single or dual fiber.

Figure 2, Mux/Demux and Mux&Demux in single fiber

Figure 3, Mux&Demux in single and Dual fiber

3.Packaging

Component, ABS box, LGX module, cassette, Rack mounted, the choice is depending on your application, where you want to put it in.

Figure 4, Some packaging of WDM Multiplexer

4.Additional Ports

MON(Monitoring port) allow you to monitor what is being received and transmitted on the Common port. EXP(Express port) provide further expansion of CWDM channels or integration of other wavelengths used in the 1260-1520&1570-1635nm wavelength range. UPG(Upgrade port) is to expand on your existing DWDM network of expand into using DWDMs from your CWDM network.

Table 1, Some definition of additional ports of WDM Multiplexer

Figure 5, Some application of additional ports of WDM Multiplexer

5.Connectors

LC/UPC in transmission network and datacenter, SC/APC in PON access network, are the common choice, but there are much more connector types you need to know, although some of them you will never see.

 Figure 6, Some types of optical connector

6.Others

Congrats, after above 5 points, you can talk the cost with your client or vendor. Before the production, there are still some points that need to know, the performance(especially the insertion loss, if there is any special demand), the fiber characteristics(pigtail length, jacket, color, core media...), and others if you want to talk.

All knowledge are in “Order Information”.

For more information, visit Etern Optoelectronics website: https://www.szetern.com, or email to: sales@szetern.com