TP-Link TL-SM321B Gigabit WDM Bi-Directional SFP Module 20KM Price in Kenya

The TP-Link TL-SM321B is a 1000Base-BX WDM Bi-Directional SFP transceiver designed to transmit Gigabit Ethernet over a single strand of single-mode fibre.

Instead of requiring two fibre cores for separate transmit and receive signals, the TL-SM321B uses Wavelength Division Multiplexing (WDM). It transmits at 1310nm and receives at 1550nm, allowing both directions of data to share one optical fibre when paired with the complementary TP-Link TL-SM321A.

Current TP-Link documentation specifies 1.25Gbps, 9/125µm single-mode fibre, LC simplex connectivity and a maximum transmission distance of up to 20km. The module also supports DDM, SFP-MSA and hot-swappable operation. 

TP-Link TL-SM321B Specifications

TP-Link's current SM321B specification confirms Tx 1310nm / Rx 1550nm, 20km reach, LC simplex interface, 1.25Gbps data rate, DDM, SFP-MSA and hot-swappable operation.

What Is the TP-Link TL-SM321B?

The TL-SM321B is a compact optical transceiver installed in a compatible Gigabit SFP slot.

It converts electrical Gigabit Ethernet signals into optical signals for transmission over single-mode fibre.

A typical network connection is:

Switch A → TL-SM321A → Single Fibre → TL-SM321B → Switch B

The A and B modules use opposite transmit and receive wavelengths, allowing full-duplex communication through one fibre strand.

What Does WDM Mean?

WDM stands for:

Wavelength Division Multiplexing

WDM technology allows different optical wavelengths to travel simultaneously through the same fibre.

For the TP-Link TL-SM321A and TL-SM321B pair:

TP-Link specifically states that the TL-SM321B is designed to work with the TL-SM321A as a complementary pair. 

What Is a Bi-Directional SFP?

A Bi-Directional SFP, commonly called BiDi, transmits and receives optical data through a single fibre strand.

A conventional duplex SFP normally requires:

Core 1 → Transmit

Core 2 → Receive

A BiDi SFP instead uses:

One Fibre Core → Transmit + Receive

by assigning different wavelengths to each direction.

This can significantly reduce the number of fibre cores required in a network.

1000Base-BX Gigabit Ethernet

The TL-SM321B is based on the 1000Base-BX concept for Gigabit Ethernet transmission over single-mode fibre.

TP-Link describes the module as a 1000Base-BX WDM Bi-Directional SFP Module. 

It is suitable for:

• Switch-to-switch connections

• Fibre media converters

• Building-to-building links

• ISP distribution

• CCTV fibre networks

• Campus networks

• Enterprise fibre infrastructure

1.25Gbps Data Rate

The TL-SM321B operates at an optical data rate of:

1.25Gbps

This supports standard Gigabit Ethernet communication.

TP-Link specifies a data rate of 1.25Gbps for the current 20km model.

1310nm Transmit Wavelength

The TL-SM321B transmits optical data at:

1310nm

This signal travels toward the complementary TL-SM321A module.

The TL-SM321A is designed to receive at 1310nm.

1550nm Receive Wavelength

The TL-SM321B receives data at:

1550nm

The complementary TL-SM321A transmits at 1550nm.

Therefore:

TL-SM321B:
Tx → 1310nm
Rx ← 1550nm

TL-SM321A:
Tx → 1550nm
Rx ← 1310nm

This complementary wavelength arrangement enables bidirectional transmission through one fibre. 

TL-SM321B and TL-SM321A Pairing

The correct pairing is:

TL-SM321A ↔ TL-SM321B

A typical connection is:

Switch / Media Converter
↓
TL-SM321A
↓
Single-Mode Fibre
↓
TL-SM321B
↓
Switch / Media Converter

TP-Link specifically recommends using the complementary A and B modules together. 

Can Two TL-SM321B Modules Work Together?

Normally, no.

Two TL-SM321B modules would both:

• Transmit at 1310nm

• Receive at 1550nm

The wavelengths would therefore not be complementary.

For a standard TP-Link BiDi link, use:

TL-SM321A at one end

and

TL-SM321B at the other end.

Single-Fibre Gigabit Ethernet

One of the biggest advantages of the TL-SM321B is that it requires only:

One Fibre Strand

This is particularly valuable where fibre cores are limited.

For example, conventional duplex modules need:

2 fibre cores per link

while BiDi modules need:

1 fibre core per link

This can effectively increase the number of independent Ethernet links that can be carried over an existing fibre cable.

Up to 20KM Transmission Distance

Current TL-SM321B versions support transmission distances of up to:

20 kilometres

over:

9/125µm Single-Mode Fibre

TP-Link lists 20km as the maximum cable length for current SM321B versions. 

Actual achievable distance depends on total optical loss across the fibre route.

Older TL-SM321B Versions

Not every TL-SM321B hardware revision has identical specifications.

For example, an older TP-Link V2 page lists a 10km maximum distance, while current versions specify 20km. 

TL-SM321B Distance by Version

For installations exceeding 10km, always check the exact hardware revision and product label.

LC Simplex Connector

The current TL-SM321B uses:

LC Simplex

This means only one LC fibre interface is required.

TP-Link's current SM321B specifications identify the connector as LC Simplex. 

Some older TL-SM321B documentation identifies the port as LC/UPC, reflecting earlier product revisions. 

LC Simplex vs LC Duplex

Watch TP-Link TL-SM321B Video

https://youtu.be/RsN1tmrsrNE

The TP-Link TL-SM321B is particularly useful in fibre networks where available cores are limited. Its WDM design allows both transmit and receive signals to travel through a single fibre strand, reducing the amount of fibre required for each Gigabit Ethernet link.

When paired with the complementary TL-SM321A, the B module transmits at 1310nm and receives at 1550nm, while the A module performs the reverse. This wavelength pairing provides simultaneous bidirectional communication across the same single-mode fibre.

The module's combination of 20km reach, 1.25Gbps data rate, LC simplex interface, DDM support and hot-swappable SFP design makes it suitable for enterprise, ISP, CCTV, campus and building-to-building fibre networks. 

Digital Diagnostic Monitoring – DDM

Current TL-SM321B modules support:

DDM – Digital Diagnostic Monitoring

DDM allows compatible switches and network equipment to monitor transceiver operating information.

Depending on the networking platform, this can include:

• Transmit optical power

• Receive optical power

• Module temperature

• Supply voltage

• Laser bias current

• Diagnostic alarms

TP-Link confirms DDM support on current SM321B versions. 

Why Is DDM Useful?

DDM can help technicians diagnose fibre problems without immediately disconnecting the link.

For example, unusually low receive power may indicate:

• Excessive fibre attenuation

• Dirty connectors

• Poor fusion splices

• Damaged fibre

• Fibre bends

• Incorrect patch cords

• A long route approaching the optical limit

SFP-MSA Compatibility

The TL-SM321B supports:

SFP-MSA

or:

Small Form-factor Pluggable Multi-Source Agreement

TP-Link confirms SFP-MSA support on the current SM321B. 

This standard defines the physical and electrical characteristics of the SFP interface.

However, individual switch manufacturers may apply their own compatibility requirements.

Hot-Swappable Design

The TL-SM321B is:

Hot-swappable

This allows the module to be inserted or replaced in supported equipment without replacing the entire switch or media converter.

TP-Link lists hot-swappable operation among the module's hardware features.

TP-Link TL-SM321B for TP-Link Switches

The TL-SM321B can be used with compatible TP-Link switches equipped with Gigabit SFP ports.

Typical applications include:

• Core-to-access switch links

• Distribution switches

• Fibre aggregation

• Building uplinks

• Remote cabinets

• Campus links

TP-Link lists compatibility with its Gigabit SFP-equipped networking equipment and recommends TP-Link modules for TP-Link devices. 

TP-Link TL-SM321B with MC220L

The TP-Link MC220L is a Gigabit media converter with an SFP slot.

TP-Link specifically lists the MC220L among compatible products for the TL-SM321B. 

A typical configuration is:

Copper Ethernet
↓
MC220L
↓
TL-SM321A
↓
Single Fibre
↓
TL-SM321B
↓
Remote SFP Switch

TL-SM321B for Building-to-Building Links

The module can connect buildings through existing single-mode fibre infrastructure.

Example:

Building A
↓
Switch + TL-SM321A
↓
Single Fibre Core
↓
Switch + TL-SM321B
↓
Building B

This is useful in:

• Schools

• Universities

• Business parks

• Hospitals

• Factories

• Estates

• Hotels

• Government compounds

TL-SM321B for ISP Networks

ISPs can use TL-SM321A/TL-SM321B pairs for point-to-point Gigabit links including:

• POP-to-POP links

• Distribution switches

• Tower connections

• Enterprise customer links

• Access networks

• Estate fibre

• Remote cabinets

The use of one fibre instead of two can conserve valuable fibre capacity.

TL-SM321B for CCTV Networks

The TL-SM321B is also suitable for transmitting aggregated CCTV traffic over fibre.

Typical layout:

IP Cameras
↓
PoE Switch
↓
TL-SM321A
↓
Single-Mode Fibre
↓
TL-SM321B
↓
Core Switch
↓
NVR

This is useful in installations where camera systems span large distances.

TL-SM321B for Campus Fibre Networks

Campus networks often need to connect several separate buildings.

Instead of running copper Ethernet between buildings, fibre offers:

• Greater transmission distance

• Electrical isolation

• Resistance to electromagnetic interference

• Gigabit bandwidth

• Better scalability

• Reduced fibre-core usage when BiDi modules are used

TL-SM321B vs TL-SM321A

These two modules are complementary.

The complementary wavelength pairing is the most important difference. 

TL-SM321B vs TL-SM311LS

Both modules are intended for Gigabit single-mode fibre networks, but they use different fibre configurations.

TL-SM321B vs TL-SM311LM

TL-SM321B vs Standard 20KM SFP

TL-SM321B vs 10G BiDi SFP+

The TL-SM321B is a 1 Gigabit SFP, not a 10G module.

TL-SM321B vs TL-SM321B-2

TP-Link also produces shorter-distance versions.

The TL-SM321B-2 is a 2km BiDi module, while the standard TL-SM321B is designed for up to 20km.

The complementary pairings are:

TL-SM321A ↔ TL-SM321B for 20km

TL-SM321A-2 ↔ TL-SM321B-2 for 2km.

Why Use a BiDi SFP?

The primary advantage is:

Fibre Core Conservation

Consider a 12-core single-mode fibre cable.

With conventional duplex modules:

12 cores ÷ 2 = 6 fibre links

With BiDi modules:

12 cores = potentially 12 point-to-point fibre links

Actual deployment depends on network topology, but BiDi can significantly improve fibre utilization.

Optical Budget for a 20KM Link

The rated 20km reach does not mean every physical 20km fibre link will automatically work.

Total link loss includes:

Fibre attenuation + Connector loss + Splice loss + Patch-cord loss + Engineering margin

Problems that can reduce reach include:

• Dirty connectors

• Poor fusion splices

• Damaged fibre

• Excessive bends

• Too many connectors

• Bad adapters

• High fibre attenuation

Fibre Connector Cleaning

LC connectors should be cleaned before insertion into the SFP.

Contamination can cause:

• High attenuation

• Low received optical power

• Link flapping

• Packet loss

• Complete link failure

A fibre cleaning pen or suitable lint-free cleaning system can be used.

Testing a TL-SM321B Fibre Link

Optical Power Meter

An Optical Power Meter can measure the amount of optical signal reaching the receiver.

OTDR

An OTDR can help locate:

• Fibre breaks

• Splice losses

• Connector reflections

• Macrobends

• Excessive attenuation

• Total fibre length

VFL

A Visual Fault Locator can assist with basic continuity testing and identifying visible fibre faults on shorter routes.

Operating Temperature

Current TP-Link specifications give the TL-SM321B an operating range of:

0°C to 70°C

with storage conditions of approximately:

-40°C to 85°C.

TL-SM321B Dimensions

TP-Link lists approximate dimensions of:

55.4 × 14.6 × 12.9mm

for the current module. 

TP-Link TL-SM321B Price in Kenya

The price of the TP-Link TL-SM321B Gigabit WDM Bi-Directional SFP Module 20KM in Kenya varies according to supplier, hardware revision, stock availability, VAT and whether the module is purchased individually or as part of an A+B pair.

Current Kenya-accessible retail listings confirm availability of the 20km TL-SM321B, although some suppliers may show the product as temporarily out of stock.

Because the module is normally paired with the TL-SM321A, customers should confirm whether a quoted price covers:

One TL-SM321B module

or

One complete TL-SM321A + TL-SM321B pair.

Contact Fiber Optics Kenya for the current TL-SM321B price in Kenya.

What Affects TL-SM321B Price in Kenya?

Pricing can vary according to:

• Hardware revision

• 10km or 20km version

• Supplier

• Warranty

• VAT

• Import cost

• Stock availability

• Quantity ordered

• Whether the TL-SM321A is included

• Original TP-Link distribution source

Is TL-SM321A Included with TL-SM321B?

Normally, each SFP module is supplied individually.

TP-Link's package contents for the TL-SM321B specify:

• TL-SM321B SFP Module

• Installation Guide 

Therefore, the TL-SM321A required at the opposite end is usually purchased separately unless the supplier specifically sells them as a pair.

How to Choose the Correct TL-SM321B

Before ordering, verify:

1. The equipment has a compatible Gigabit SFP port.

2. The installed cable is 9/125µm single-mode fibre.

3. You require a single-fibre BiDi link.

4. The opposite end uses the complementary TL-SM321A.

5. The module is the required 20km version.

6. The optical connector is LC simplex.

7. The total fibre distance is within the optical budget.

8. Your switch or media converter supports the SFP.

9. DDM support is available if diagnostic monitoring is required.

Recommended Accessories

Frequently Asked Questions About TP-Link TL-SM321B

What is the TP-Link TL-SM321B?

It is a 1000Base-BX WDM Bi-Directional Gigabit SFP module designed for single-mode fibre. 

Is TL-SM321B a Gigabit SFP?

Yes.

What is its optical data rate?

1.25Gbps. 

What Ethernet speed does it provide?

1 Gigabit Ethernet.

What wavelength does TL-SM321B transmit?

1310nm. 

What wavelength does TL-SM321B receive?

1550nm.

Which module pairs with TL-SM321B?

The TP-Link TL-SM321A. 

What wavelength does TL-SM321A transmit?

1550nm.

What wavelength does TL-SM321A receive?

1310nm.

Can I connect TL-SM321B to another TL-SM321B?

Normally no. Their Tx and Rx wavelength assignments are the same rather than complementary.

Can TL-SM321B connect to TL-SM321A?

Yes. That is the intended pair. 

What does BiDi mean?

Bi-Directional optical communication over one fibre strand.

What does WDM mean?

Wavelength Division Multiplexing.

How many fibre strands does TL-SM321B need?

One.

What type of fibre does it use?

9/125µm single-mode fibre. 

What is the maximum transmission distance?

Current versions support up to 20km. 

Why do some TL-SM321B specifications say 10km?

Older hardware revisions were rated differently. TP-Link's older V2 documentation lists 10km while current versions list 20km.

Should I check the hardware revision?

Yes, particularly if the fibre link exceeds 10km.

What connector does TL-SM321B use?

Current versions use LC Simplex. 

Does it use LC/UPC?

Older TP-Link versions list LC/UPC, while current SM321B documentation specifies LC Simplex. 

Is the connector duplex?

No. The current module uses a simplex optical interface.

Does TL-SM321B require two fibre cores?

No.

Can it help save fibre cores?

Yes. This is one of the main advantages of WDM BiDi modules.

Does it support DDM?

Yes. 

What is DDM?

Digital Diagnostic Monitoring.

What can DDM monitor?

Depending on the host equipment, parameters may include optical power, temperature, voltage and laser operating information.

Is it SFP-MSA compatible?

Yes. 

Is it hot-swappable?

Yes. 

What voltage does it use?

3.3V. 

Can it work with TP-Link switches?

Yes, with compatible Gigabit SFP-equipped TP-Link switches.

Can it work with TP-Link MC220L?

Yes. TP-Link lists MC220L compatibility.

Can it work with other switch brands?

Potentially, but TP-Link warns that compatibility with third-party equipment may vary.

Is it suitable for ISP networks?

Yes.

Is it suitable for CCTV networks?

Yes.

Is it suitable for enterprise networks?

Yes.

Is it suitable for campus fibre?

Yes.

Can it connect two buildings?

Yes.

Can it work over 5km?

Yes, provided the link remains within the optical power budget.

Can it work over 10km?

Yes for the 20km-rated current version.

Can it work over 15km?

Potentially, provided the total optical loss remains within specification.

Can it work over 20km?

Current versions are rated up to 20km over suitable single-mode fibre. 

Can it work over 40km?

No. A suitably rated 40km BiDi SFP pair should be used.

Is TL-SM321B the same as TL-SM321B-2?

No. TL-SM321B-2 is designed for shorter, approximately 2km links. 

Which module pairs with TL-SM321B-2?

TL-SM321A-2.

Is TL-SM321B a single-mode SFP?

Yes.

Can it work with multimode fibre?

It is designed for 9/125µm single-mode fibre.

Can I use OS2 fibre?

Yes.

Is TL-SM321B the same as TL-SM311LS?

No.

What is the difference between TL-SM321B and TL-SM311LS?

TL-SM321B uses single-fibre WDM BiDi, while TL-SM311LS uses a conventional duplex fibre connection.

Is TL-SM321B the same as TL-SM311LM?

No. TL-SM311LM is a multimode 850nm SFP for shorter distances.

Is TL-SM321B a 10G module?

No. It is a Gigabit module.

Is TL-SM321B an SFP+ module?

No. It is an SFP module.

Can I use it for 10Gbps?

No.

Can I use an LC-LC simplex patch cord?

Yes.

Can I use LC-SC simplex fibre?

Yes, if the remote termination, polish and fibre type are compatible.

Should the patch cord be single mode?

Yes.

Do I need a duplex patch cord?

No. BiDi operation requires a simplex connection.

Should I clean the LC connector before installation?

Yes.

Can a dirty connector cause link failure?

Yes.

Can an Optical Power Meter test the link?

Yes.

Can an OTDR test the fibre route?

Yes.

What is the operating temperature?

Current TP-Link documentation specifies 0°C to 70°C. 

What is the storage temperature?

Current versions specify approximately -40°C to 85°C. 

What are its dimensions?

Approximately 55.4 × 14.6 × 12.9mm. 

Is TL-SM321A included with TL-SM321B?

Normally no. TP-Link's package contents list the TL-SM321B module and installation guide. 

Do I need to buy TL-SM321A separately?

Usually yes, unless the supplier is selling the two modules as a complete pair.

What is the TP-Link TL-SM321B price in Kenya?

The price varies according to supplier, stock, hardware revision, VAT and whether you are buying one module or a complete A+B pair.

Do you supply TL-SM321A and TL-SM321B pairs?

Yes, subject to stock availability.

Do you supply 20KM BiDi SFP modules?

Yes.

Do you supply 40KM BiDi SFP modules?

Yes.

Do you supply single-mode fibre patch cords?

Yes.

Do you supply TP-Link media converters?

Yes, subject to availability.

Do you supply Optical Power Meters?

Yes.

Do you supply OTDRs?

Yes.

Can ISPs order SFP modules in bulk?

Yes. Bulk orders are suitable for ISPs, enterprises, fibre contractors, CCTV integrators and campus networks.

Do you deliver outside Nairobi?

Yes. Fiber Optics Kenya supplies fibre optic and networking equipment throughout Kenya.

Why Buy TP-Link TL-SM321B from Fiber Optics Kenya?

Contact Fiber Optics Kenya

Fiber Optics Kenya
Lyric House, 7th Floor Room S9
Kimathi Street, Nairobi

Phone: +254 704 991 492
Email: info@fibreopticskenya.co.ke

The TP-Link TL-SM321B Gigabit WDM Bi-Directional SFP Module 20KM is designed for Gigabit Ethernet transmission over one 9/125µm single-mode fibre strand. Current versions support 1.25Gbps, Tx1310nm/Rx1550nm, LC simplex connectivity, DDM, SFP-MSA and hot-swappable operation, with transmission distances up to approximately 20km. 

Its primary advantage is efficient fibre usage. When paired with the complementary TP-Link TL-SM321A, the two SFP modules use different wavelengths in opposite directions, allowing full-duplex Gigabit communication over a single core rather than the two cores required by conventional duplex SFPs. 

The module is therefore well suited to ISP networks, enterprise fibre, CCTV backbones, campus connections, estate networks and building-to-building links, particularly where available fibre cores are limited.

Contact Fiber Optics Kenya for the current TP-Link TL-SM321B price in Kenya, TL-SM321A/TL-SM321B pairs, 20KM and 40KM BiDi modules, LC simplex patch cords, media converters, fibre testing equipment, bulk orders and nationwide delivery.