Introduction to Fiber Optics for 10G Network at Home

Fiber optics are becoming cheaper and more affordable for homes nowadays, and they could be a fantastic alternative for RJ-45 10GBase-T Ethernet. Fiber transceivers at the same speed use less power and run cooler. They also don't need to be upgraded like you would need to upgrade an Ethernet cable from Cat5e to Cat6a to now Cat8.

I have worked with fiber network designs at work, at least in theory. But in the last two weeks, I learned even more than I cared for about fiber optics, and here is a quick summary about them before I forget.

• Fiber core size: single-mode fiber (SMF, OS2) vs. multimode fiber (MMF, OM5, OM4, OM3, OM2, OM1).
• Single mode has a smaller core and can run for longer distances. Multimode fibers may be more cost effective once upon a time, but these days single mode fibers are so cheap, they should be the default choice for even short (< 100m) runs.
• Note: the mode type must match with the transceiver as well, so you have to use a single mode fiber with a single mode transceiver.
• Number of strands: simplex (1 fiber) or duplex (2 fibers).
• The transceivers most commonly used for data center applications will use duplex fibers, using one strand for each direction of transmission. Both directions typically use the same wavelength.
• Simplex fibers are more common for Fiber To The Home (FTTH). You have to use a matching (opposite) pair of transceivers at the two ends, e.g. one side is 1330nm-TX/1270nm-RX, and the other side should be 1270nm-TX/1330nm-RX. The two wavelengths traverse on the same fiber strand.
• Connector type: SC (standard connector, larger) vs. LC (lucent connector, smaller).
• For some reason, the LC transceivers are more commonplace, possibly because you can fit a duplex connector into a transceiver with the SFP form factor.
• There are also SC transceivers, but these are less common.
• Again, you have to match the connector with the transceiver.
• Connector contact type: UPC (domed, color coded blue) vs. APC (angled, color coded green). They refer to how the fiber ending is terminated. The angled type reduces back-reflection.
• You have to match the contact type with the transceiver as well. Inserting APC connector to a UPC transceiver can damage the optics.
• I typically find either SC/APC or LC/UPC to be more common. The other combinations (e.g. SC/UPC or LC/APC) are possible but uncommon.
• Adapters exist but they can cause signal loss. Due to the naming, it can be hard to find the correct adapter by keyword (e.g. "SC/APC female to LC/UPC male" can also give you results for "SC/APC male to LC/UPC female").
• Sometimes SC/APC is written as SC/Angled or simply SCA.

Bend radius: more recently, I learned about bend insensitive fibers from a video about the InvisiLight fiber kit. The whole kit cost $250 and includes a pre-terminated G.657.B3 simplex fiber, two 1G transceivers, and two media converters. For my purpose, I would need to buy my own 10G transceivers and a 10G media converter.

Bend insensitive fibers are characterized by having smaller bend radius than the regular fibers (30mm), and they are defined by the standards G.657.A1 (10mm), G.657.A2 or B2 (7.5mm), and G.657.B3 (5mm). This primarily allows installation in tight corners in the home, and the transceivers are agnostic to the bend radius.

FS.com has a custom fiber builder where you can build simplex or duplex fibers with custom core sizes, connector and contact types, and bend radius. They offer white color which is better than bright yellow for home installation. However, their sales representative told me that G.657.A2 with 0.9mm cable diameter has a minimum order quantity (MOQ) of 1KM (this is not on the website). The best they could do with no MOQ is G.657.A1 with a 2.0mm diameter.

There appears to be some pre-terminated G.657.A2 0.9mm cables on eBay, but I have not tested them. Some of the fibers on eBay are also a bit weird, having SC/APC (green) on one side and SC/UPC (blue) on the other, or they are from SC to LC. Either way, a 40 meter (130 feet) long bend insensitive fiber cable should be in the $12-$16 range. Fiber is cheaper than Cat6 per unit length, and they are not limited to 100 meters.

For running between rooms in the home, you would typically use a simplex single-mode and matching LC/LC or SC/SC transceivers, and choose or build a fiber cable with the same connector. Here are some transceiver options I found:

• LC/UPC single-mode simplex:
• Elfcam branded 10G LC Bidi transceivers (20km), sold as a matching pair for $55.
• FS.com branded 10GBASE-BX BiDi transceivers (options from 10km to 100km). Here you have to buy two separate transceivers with matching opposite TX/RX frequencies. A pair of 10km would cost $100.
• Ubiquiti branded 10G LC Bidi transceivers (6.2 miles, or 10km), also sold as a matching pair for $160.
• SC/APC single-mode simplex: Elfcam branded 10G SC Bidi transceivers (20km), also sold as a matching pair for $66.

A distance of 10km / 6.2 miles will let you run fiber to your friend's house living in the next town!

For running short distances between devices in the rack room, LC duplex single-mode has more transceiver options. I also use a Direct Attached Cable, which is just copper but with both ends hard-wired to SFP+ connector.

The SFP+ connector refers to the plug form factor where the transceiver is inserted into the switch device. It typically determines the speed as well.

• SFP: 1G.
• SFP+: 10G, 25G.
• QSFP (or QSFP28, literally "quad SFP"): 100G.
• QSFP-DD (or QSFP56, literally "double density quad SFP"): 400G, 800G.
• OSFP (literally "octa SFP"): 400G, 800G.

With data centers upgrading from QSFP 100G to QSFP-DD or OSFP 400G or 800G to satisfy the AI computing needs, and with more FTTH deployments, we are seeing more surplus SFP+ 10G transceivers and switches flowing to the consumer market. This could be a good time to upgrade your home network cabling from copper based cable to fiber.